Here is an announcement from SolidWorks:
Notice: SolidWorks 2008 will block the loading of 3rd party SolidWorks add-ins created using the old style MFC 4.2 extension DLL architecture.
Testing of SolidWorks 2008 has revealed severe instability with add-ins created using this architecture.
Users will see the following message when attempting to load an add-in using this old architecture: " is incompatible with this version of SolidWorks and cannot be loaded. Check with vendor for compatibility information."
This will affect any Solution Partner or internally developed add-in products using MFC 4.2 extension DLL architecture when used in conjunction with SolidWorks 2008. This does not affect SolidWorks 2007 and earlier releases.
This does not affect add-ins created in VB, VB.Net, C# or those communicating with SolidWorks via the COM interface.
Please direct questions to your local support provider.
Take note that CAMWorks 2007 WILL NOT run in SolidWorks 2008. If you try SolidWorks will immediately shut down.