Can't reset PRAM and reinstall OS! I have a problem with my MacBook Pro 2010 13 inch, 2.4 GHz. Originally I had Snow Leopard installed on my Mac, then I was trying to upgrade it to Lion (official version from App Store). 

During the installation, an error occurred and I got a kernel panic. But that's not exactly the problem. I found out that the laptop had had a firmware password set by somebody (not me). 

None of the boot modifier keys (except option) appear to work. When I press option, it asks me for a password. Some people told me to switch the RAM slots or take one out and then turn on the computer holding &#8984;+&#8997;+P+R. That didn't work either. Still see the password prompt. 

Any ideas how to reset it?
Not sure if this is too late of an answer. I know you've already attempted to disable the password, but try these steps exactly:

You can remove the firmware password by changing the RAM configuration, booting up to the startup menu, shutting down and changing it back. Basically, if you have two 1GB chips of RAM in there now, you can remove one of the chips, start up holding alt/option, shut down and put the other chip back in. This will remove the firmware password.

Now, you can follow these instructions for doing the erase and install.

Good luck!