Hashtable insert failed. Load factor too high : Dot net 4.5

I'm getting an exception “System.InvalidOperationException: Hashtable insert failed. Load factor too high.”

My application is developed in VS2010 with 4.0 framework and it is working fine in our development environment (4.0 version ) (for 4.0 framework I'm able to find the hotfix and I've installed it in my development environment). In production environment framework is upgraded to 4.5 version and we often getting the mentioned exception.

Application developed : windws 7 - 32 bit OS / vb.net 4.0
Development environment (hotfix installed) :  windows server 2008 - 64 bit  / dotnet FW 4.0
Prod Environment : windows server 2008 - 64 bit / dotnet FW 4.5 

Kindly help me resolving this issue.

Thanks.