Visual Studio has encountered a breakpoint....

OK, this one is new to me. I had selected a solution from the MRU, to open, and I got this error:


Clicking debug, indeed goes into the debugger, after telling me it's loading a ton of symbols, it tells me ( not surprisingly ) that it has no symbols for the code from within the IDE that has crashed. Has anyone seen this before ? I thought I'd seen it all, but this is news to me.