Server Error in '/' Application. <hr width="100%" size="1" color="silver" />

[A]System.Collections.Generic.Dictionary`2[System.String,Dynamic+PageConfig] cannot be cast to [B]System.Collections.Generic.Dictionary`2[System.String,Dynamic+PageConfig]. Type A originates from 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll'. Type B originates from 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll'.