Scary day for me last Thursday.
I had gone up to Brisbane, and was due to speak at the Queensland SQL User Group on Thursday night. Unfortunately, disaster struck about an hour beforehand.
Nothing to do with the recent floods (although we were meeting in a different location because of them). It was actually down to the fact that I'd been fiddling with my machine to get Virtual Server running on Windows 7, and SQL had finally picked up a setting from then.
I could run Management Studio, but it couldn't connect at all. No error, it just seemed to hang.
One of the things you have to do to get Virtual Server installed is to tweak the Group Policy settings. I'd used gpupdate /force to get Windows to pick up the new setting, which allowed me to get Virtual Server running properly, but at the time, SQL was still using the previous settings. Finally when in Brisbane, my machine picked up the new settings, and caused me pain.
Dan Benediktson describes the situation. If the SQL client picks up the wrong value out of the GetOverlappedResult API (which is required for various changes in Windows 7 behaviour), then Virtual Server can be installed, but SQL Server won't allow connections. Yay. Luckily, it's easy enough to change back using the Group Policy editor (gpedit.msc). Then restarting the machine (again!, as gpupdate /force didn't cut it either, because SQL had already picked up the value), and finally I could reconnect.
On Thursday I simply borrowed another machine for my talk. Today, one of my guys had seen and remembered Dan's post. Thanks, both of you.