"Changes are not allowed while code is running or if the option 'Break all processes when one process breaks' is disabled. The option can be enabled in Tools, Options, Debugging."
If you're like me and you've had to work with a number of different installs of VS2005 then you have probably seen prompt before. You tend to see this annoying pop-up message while you're in debugger mode and you try and modify any of the source files. All that you will need to do is to uncheck the "Enable Edit and Continue" option in Tools > Options > Debugging > Edit and Continue.
If anyone has any more info about this issue please, please leave a comment.