Workflow Debugging - Attaching to W3WP.EXE Crashes VS.NET
Marcel de Vries has a solution - in the attach dialog, only attach to Workflow instead of allowing VS.NET to automatically determine the type of code to debug. For details of Marcel's solution, click here.
I used to hit this problem time and time again, but since finding this solution and selecting only workflow when I want to debug a workflow I have yet to hit the problem - so looks like the solution works !!