Ok, many of us who have played ME1 have encountered the "Overheat Bug", where a weapon overheats and stays overheated until you save and reload the game, and it is a source of significant frustration, especially when fighting Engineers and ALL of your weapons are locked up.
The bug first appeared for people using cracked versions of the v1.00 executable. The cracking groups eventually fixed the problem, and many people still think the problem is only caused by a cracked exe. However, those with legal copies of the game started having the problem after the first DLC, "Bring Down the Sky", and the v1.01 patch were released and it didn't get better after the v1.02 patch was released. Continuing the EA (Bioware was acquired by EA by this time) tradition of horrible customer support, nothing was ever said about it.
After a great deal of searching, reading, and beating my head on the top of my desk, I've managed to pull all the threads and directions together and FIXED the Overheat Bug in my game. I have decided to put all the instructions in one place so those here can find them if needed.
Please note, if you have NEVER played ME1 without first patching it to v1.02, never started a character, never earned an Achievement, etc; you most likely have never encountered the Overheat bug and this will be of little use to you.
It turns out that the Overheat Bug is caused, somehow, by a corrupted profile...file, seemingly tied to the "Dog of War" and "Geth Hunter" Achievements. This is how you fix it.
Step 1: Backup your Profile.
Go to your save directory located here (note that "X:" is the letter of the drive windows is installed on):
* On Windows XP/2000: X:\Documents and Settings\[username]\My Documents\BioWare\Mass Effect
* On Windows Vista/7: X:\Users\[username]\Documents\BioWare\Mass Effect
Make a copy the file "Profile.MassEffectProfile" to backup you profile just in case. Better safe than sorry.
Step 2: Enable the Console.
Follow the instructions [url="http://masseffect.wikia.com/wiki/Console#Enabling_The_Console"]HERE[/url] to enable the console. Load the game. Once at the Main Menu, press whatever key you assigned to the console. If the console opens (it's very obvious), you did it right.
Step 3: Save your Achievements.
From the Main Menu, click "Options", then click "Achievements". Write down all of the Achievements you have earned. Depending on how long you have been playing the game, it may be easier to write down the ones you don't have (for example: there are 50 Achievements and I have about 45 of them).
Step 4: Delete your old Profile.
Remember the file you make a backup of in Step 1? Go back to that directory and DELETE the ORIGINAL file. Keep the backup, but make sure it has a different name, or is in a different directory.
Step 5: Create a new Profile.
This is done simply: Load the game. When the game loads (be patient, it may take longer than normal), and you see the Main Menu, you will see a "Saving Content" (or something similar) line. This is the game creating a new profile file. When it finishes, you ready for the next step.
Step 6: Reload character save profiles.
From the Main Menu, click "Load Career". You will notice none of your characters are listed, don't worry, we are going to fix that. Click "Switch Career", and then "All Careers". You will now see all of your saves, from all of your characters, listed. Pick a save from one character and load it. That character will now have it's profile restored. Repeat the process for each of your characters.
Step 7: Restore your Achievements.
You could replay the game four or five times to re-earn your Achievements, but let's face it, it would be a tedious pain in the backside. That's why we enabled the Console. From the Main Menu, open the console. Use the command "UnlockAchievement n" (without the quotes), where "n" is the Achievement's number code. The number codes for the Achievements can be found [url="http://masseffect.wikia.com/wiki/PC_Cheats#Achievement_Codes"]HERE[/url].
Once you finish restoring your Achievements, you should have your game back to the way it was, and you should no longer encounter the Overheat Bug.
Mass Effect Overheat Bug and How to Fix It!
Ok, if some of you are wondering if this actually works or not, I have a report.
I have played a character after fixing my profile. I have completed Eden Prime, the Citadel (exposing Saren), Therum (finding Liara), and the Bring Down the Sky DLC. Between by over-developed trigger finger, Batarian Engineers (and thier love of the "Sabotage" power), and Geth Sappers I have overheated my weapon literally dozens of times and not once did it lock up permanently.
This works people.
I have played a character after fixing my profile. I have completed Eden Prime, the Citadel (exposing Saren), Therum (finding Liara), and the Bring Down the Sky DLC. Between by over-developed trigger finger, Batarian Engineers (and thier love of the "Sabotage" power), and Geth Sappers I have overheated my weapon literally dozens of times and not once did it lock up permanently.
This works people.
The last time I played, I didn't encounter this bug, but thanks for posting these tips anyway. 
''They say truth is the first casualty of war. But who defines what's true? Truth is just a matter of perspective. The duty of every soldier is to protect the innocent, and sometimes that means preserving the lie of good and evil, that war isn't just natural selection played out on a grand scale. The only truth I found is that the world we live in is a giant tinderbox. All it takes...is someone to light the match" - Captain Price
Ok, there is a small issue with fixing the overheat bug this way.
Even if you set the "Power Gamer" (reach level 50) and the "Extreme Power Gamer" (reach level 60) achievements, it still doesn't count them and your next new character will be capped at Level 50 the first play through.
This, in my opinion, is a small problem, considering the one it fixes.
Even if you set the "Power Gamer" (reach level 50) and the "Extreme Power Gamer" (reach level 60) achievements, it still doesn't count them and your next new character will be capped at Level 50 the first play through.
This, in my opinion, is a small problem, considering the one it fixes.