i have exactly the same problem, win 7 64bit.
Tried to reinstall but not resolved.
I cannot open my wallet anymore. It first happened a few days ago, and I haven't been able to since. When I double-click the icon on the desktop (targets the wallet file, has always worked) nothing happens. All I see is that the computer hourglass (or circle as it is now) shows for five seconds, then nothing.
I use Win7, 64bit.
My wallet has roughly 300 transactions and 100 addresses used. Other wallets open as normal.
I have the same wallet on another machine. It works there, albeit slowly.
I guess the problem is that too many transactions clog the program. But why does it not open at all?