So just to clarify...
1) you click on your User CP link
2) on the left hand side of your screen under the Settings and Options you click on the Edit Signature link and you get an error occurred?
If this is the case then it's likely there is something going on with your computer as I can get into the Edit Signature screen without any problems. What web browser are you using? Firefox, Internet Explorer, or something different? What version is your web browser?