For the past few weeks, I receive the same error message whenever I open Trados Studio (2011). I click on OK and Trados then opens as usual, with the only difference being that my existing list of Translation Memories (to select from when opening a new document/project) had been wiped clear so I have to re-add existing TMs (which isn't really a bad thing as it was getting a bit unwieldy, as you can't sort/organise the memories).
Apart from the disappeared TMs, there is no noticeable change in functionality, but it's annoying that the error message comes up each time I open Trados. Any ideas how to rectify it?

I don't seem to be able to attach a screenshot, but the details begin with:

"An unexpected error has occurred while loading the application plug-ings."

[more details]
"MS.Internal.IO.Packaging.CustomSigned XML.GetNetFxSecurityRegistryValue(System.String.Int64)"
Type: "System.MethodAccessException, mscorlib, Version=2.0.0.0 Culture =neutral, PublicKeyToken=b77a5c561934e089"
Source:"WindowsBase"

Thanks for any help,
Glyn