I have one Single working now under CGminer 2.4.2 and before 2.4.1 without any problems, but I use Windows Server 2003
Lucky you. 2.4.1 and 2.4.2 has the same error handling with regards to this issue.
FWIW:
I have a Win7/x64 rig with (1) 5870 and (5) BFL Singles running 2.4.1 for over two weeks without issue. None of them have dropped offline, all are running 832 fw, CGminer says 826Mh/s.
Lots of observations coming in. Some people have trouble, some don't. With 5 Singles running for 2 weeks I would have expected the issue to crop up at least once. This is part of the reason that makes this 'issue' (or non-issue) difficult to pin down. Bottom line is that if the program is working for someone, then they have no worries. For the others experiencing issues, a workaround would seem to be switching back to 2.3.6.
This may or may not be related, but I noticed that 2.4.1+ will NOT run 15 devices. It will crash immediately. With 2.3.6 I was able to run 15 devices fine. I merely point this out as an example of something, which used to work, being inadvertently 'broken' in 2.4.1+.