webdev8183 on "Changing permalinks causes 500 Server Error"

perhaps the actual error would help narrow down the cause, try adding that to your post, did you do a google search for the error you received cause sometimes that can help with diagnosing the cause. Have you also tried rebooting your modem? temporarily disabling security software? try the steps in this article

I hope that helps you out, I can totally relate with how frustrating these issues can be especially when the computer doesn't really tell you why its sick, it just is if you know what I mean