Many times during the day some file or resource will be temporarily unavailable, but is there the next time I click.
It happens most often when running a complex sequence of programs such as a compile (MSVC), a program running within cygwin or mingw (Quartus, AVR Studio, others), or batch/make files with many "call" statements, either to Windows console programs or a bash shell. I can rerun the process and sometimes it works fine, other times it does not. I do not believe the linux-esque shells are the problem, but they are probably more vulnerable given the much greater number of calls they typically invoke.
But it also happens on rare occasion just clicking on an .xls or .doc file - "Resource temporarily unavailable". Click again and Excel or Word opens just fine.
I have removed/disabled the Logitec eyeball, the scanner daemon, and anything else that might be grabbing large chunks of memory.
I have disabled PrevX and Norton anti-virus ware.
This has been happening since I bought the computer new a couple years ago. I've been trying to fix this, but have found zero helpful information.
I believe this may be the trouble at the root of occasional hangs and aborts that occur about once a week.