Update August 29, 2013: I have reproduced this again and am attaching a full crash dump of msvsmon.
When using Visual Studio 2012 Update 1 to remote debug, the remote debugger will crash if I have a solution open when I attach.
Visual Studio immediately reports an error "The network connection to <server>:4016 has been lost. Debugging will be aborted." A few seconds later the remote server shows "Visual Studio Remote Debugging Monitor has stopped working." Interestingly enough, if I "Close the program" the monitor UI is still running.
If I attempt to attach again, I receive an error that a debugger is already attached to the process.
If I close Visual Studio and the remote debugging agent and start over - this time without opening a solution. I am able to connect without any issues.
-Client (VS) development machine is Windows 8 x64.
-Remote machine is Windows 2008R2 SP1.
-No firewall is involved.
-VS machine is on a domain, with local user account with the same credentials as domain account.
-Remote machine is on a different domain, also with a local account with the same credentials as VS local account.
-MSVSMON is running elevated as the local account
-I am attaching to IIS 7.5 (w3wp.exe) on the remote machine, using x64 Managed .NET 4.0/4.5