I recently finished working on a support case where the customer was hitting the same issue as this one:

2484841 FIX: A .NET Framework 4.0-based WPF application may stop responding if you right-click a control to open a pop-up control

but for Microsoft .NET Framework 3.0 rather than 4.0.

As the resolution of the case, a new hotfix has been produced:

2591373 FIX: A .NET Framework 3-based WPF application stops responding if you right-click a control to open a pop-up control

HTH

Doug