Thanks for getting back to me. I'm still baffled as to what's causing the problem, but one simple diagnostic is: can you set breakpoints again once you've uninstalled Reflector 7? I'd also double-check that there are no Reflector 6.x add-ins installed.
On a slightly different tack, do you have any other VS add-ins installed? I wonder if there might be some odd interaction between Reflector and another add-in. There's nothing I'm aware of that should cause a problem, but it's possible there may be something like that happening.
I'd also suggest, if you're not already using it, the 220.127.116.11 patch release, which you can get from from http://shop.reflector.net/download
One final question: which edition of VS 2010 are you using? Again, I'm not aware of any problems with specific editions, other than we don't support VS Express, but it might be helpful to know.