It does look like it's a problem with the USB key and/or driver. My recommendation is you load the latest hardware key drivers; see below links. Also, native 64-bit applications including Modelsim can only recognize one USB key at a time, although we are on the license server side here and daemons themselves are native 32-bit executables, so I wouldn't think this would be an issue. In any case, if you do have more than one USB key plugged in, you might try restarting the license manager with only the Modelsim USB key plugged in to see if that changes anything.
Download the latest licensing (includes hardware key drivers): http://supportnet.mentor.com/downloads/index.cfm?id=201211036&product=C106-S128-G159-P11292&redirected=true&reason=0
I hope that helps.