We had an issue in which the reporting services 2008 running on Windows 2008 suddenly stops responding and when we connect to reporting services it’s not responding, even the configuration manager fails to load Reporting Services Configuration in RS configuration Manager.

We explore the Reporting Services logs which generally available on below location and we found something interesting.

ERROR: Managed server timed out. Timeout=150 sec. GC extension timeout=30 sec.

%ProgramFiles%\Microsoft SQL Server\MSSQL.x\Reporting Services\LogFiles

During investigation it seems like a bug in Reporting Services; investigation reveals that the major cause for reporting services to be  unresponsive\crash was slow GC (Garbage collection- it manages the allocation and release of memory for your application). This error can be seen clearly in logs “Granting additional timeout of 30 sec.” indicates that managed server timed out while GC was in process, and so slow GC was the likely reason.

Slow GC occurs usually when you have a lot of RAM on the box and the report server process is using a lot of it. The problem is that for managed applications, a Garbage Collection (GC) occurs periodically. During a GC the process is suspended temporarily.
Resolution:

MS suggest that a long running queries\process related to SSRS must be killed from query analyzer should resolve this issue.

http://connect.microsoft.com/SQLServer/feedback/details/519612/reporting-services-2008-crashing

Resolution which worked for US

We tried several things but at last the resolution which worked for us is to apply a latest SP3 for SQL 2008, after applying latest SP the reporting service went to its normal consistent state.