I recently deployed an application to a production web farm for a client and everything has been relatively smooth, until this morning. As the work day began a strange exception began being tossed on just about every request, 'Hashtable insert failed. Load factor too high'. I have honestly never seen this before, but it seems to be a problem for unpatched versions of ASP.NET.
Todd Carter is an MSDN blogger and ran into this issue with a client back in January and seems to have the most cohesive answer to the problem. Evidently there is an outside chance of a race condition being created in the framework. There is a HotFix for the problem, but it is not really obvious from Technet. He does point us to a Knowledgebase article about the HotFix that will correct the problem.
I am hoping my client will deploy the HotFix and get their framework up to date as soon as possible. If it works I will report back!