You could try posting in the reporting services forum, maybe with a note that you realise you already posted the question once, but people might complain anyways about duplicate postings.
For what its worth, I've gotten that error before. I assume you've looked at your reporting services logfiles, mine are located at
d:\"program files"\"microsoft sql server"\msrs10_50.mssqlserver\"reporting services"\logfiles, but your installation might be different. When I looked at my error, it had much text but it boiled down to "remote server closed connection unexpectedly" and I didn't get any further than that, and I could not reliably duplicate the error.