I just want to pass on this info in case it is of some help. My browser, firefox, is set up for web development and in the error console this is what is posted when I get that internal server error 500.

[thumbstrips] [Exception... "Component returned failure code: 0x80004005 (NSERRORFAILURE) [nsIScrollBoxObject.ensureElementIsVisible]" nsresult: "0x80004005 (NSERRORFAILURE)" location: "JS frame :: chrome://thumbstrips/content/scrolling.js :: thumbstrips_skipToCurrentHelper :: line 186" data: no]

Not sure if this gives you any help but, as they say, info is power.

Tags: RedState