I am unable to run my signed, release keystore in Eclipse:
I get the error:
Keystore was tampered with, or password was incorrect
H
I am confused about what you are trying to achieve here. Is it that you just can't edit it as it is? When preparing it for delivery to the market, you would be exporting it unsigned (ie without the debug keystore).
Could it possibly be that you have the "force error when external jars..." option checked?
I third (or fourth) what others have said here about backing up and deleting the keystore at ~/.android - http://developer.android.com/guide/appendix/faq/troubleshooting.html#signingcalendar.
Assuming that you've already done so, I won't "google that for you", but it might be an eclipse problem.
Hope you get it going soon.