I am using ReSharper to run my UnitTests and get numerous BadImageFormatExceptions.
The topics I found here with a similar problem either deal with x64 Architecture and target other ReSharper version.
Here is the version information from ReSharper About Window:
JetBrains ReSharper 5 Full Edition
Build 5.0.1659.36 on 2010-04-13T02:19:06
Licensed to: XXX
Visual Studio 10.0.30319.1.
All my applications are fully 32-bit, compiled as "Any CPU" against .Net 4.0.
The test starts after 15-20 seconds delay, compared to almost immediate start if launched from the built-in Test Manager.
P.S.: If you require licence information to answer this question, please, let me know.