I have not heard of that specific error, but after some searching
found this posting on the MSDN forums that might help:
http://social.msdn.microsoft.com/Forums/en-US/sqlreportingservices/thread/e90c853b-6018-41b0-9dd1-abd2ac872f16
I had SSRS2005 working on my Vista box, but I never tried to get
SQL2008 setup on it. I know that SSRS2008 works fine in Server 2008
and Windows 7 (after getting things setup running IE in administrator
mode).
The other thing that I am wondering is if the version of SQL Server
2008 Express that you installed has SSRS included. As far as I know
only SQL Server 2008 Express with Advanced Services actually includes
SSRS. See this link from Microsoft that shows what is included with
each version of Express and has the appropriate download links:
http://www.microsoft.com/express/sql/download/
Hope this helps.
Steve