Microsoft.ReportingServices.ProcessingObjectModel Error

I have been creating reports using VS2005 and deploying to SQL 2005 without any problems.

Today I created 2 reports, build, deploy fine. When I created the third the deploy failed with:

Each report within VS2005 has the error "An unexpected error occurred in Report Processing."

Removing the third report didn't help, removing all reports allowed me to deploy a shared datasource. When in SQL Management Studio (Reporting Services), I get the same error when trying to import the .RDL file. I have 200GB free on the SQL disk and have increased the disk allocation for RS and RSTemp DBs.

I have tried opening permissions (unlikely as it is to be the source of the issue) and rebooted to a clean environment to rule out memory issues.

I have completely stuck, my next recourse is to re-install SQL/RS but clearly that is a last resort and not guaranteed to solve the problem either.

There looks to be an issue with and assembly DLL but there have been no mods to my environment and no MS Updates either...

I am really struggling and hope someone can come up with some ideas I haven't tried.

Thanks in advance