Well I put up a pull request that might be related to this ... then spent a day arguing with Luke-jr coz he saw it as a problem in BFGMiner ... and I still have no idea why he has any say in what goes into the BFL code in cgminer ...
(what a fucking waste of time that was)

https://github.com/ckolivas/cgminer/pull/215
(fun read that )

Anyway, the change relates to 3 issues, the 3rd one I haven't confirmed if it fixes it yet or not.
1) BFL doesn't display an ERR (only a DEBUG message) if it fails to open a device (so you don't know unless you have debug on)
2) Telling cgminer that a device is a 'bitforce:' or an 'icarus:' doesn't stop it from trying to open an invalid device name (and ignoring the error)
3) I think 2) may be the cause of getting an error on windows7 64bit where it's running in 32bit emulation and has a limit to the number of USB ports that can be opened and I think that opening an invalid device that includes something that looks like a USB port in the name may use up the limited number of available USB ports in 32bit mode

The reason why it's changed between 2.3.6 and 2.4.2 (other than that change listed above by P_Shep) is that the lead dev wanted me to include a change from BFGMiner into cgminer that Luke-jr did to resolve an issue he had with the BFL code hanging on opening an Icarus
He was given an Icarus and then put in a change to attempt Icarus first before BFL rather than fix the BFL problem.
As you can see from the minor and simple change request I made above, it is no point me even trying to fix BFL problems ...

I've also told him a simple change to BFL to match like I did in Icarus regarding aborting work on an LP (instead of hashing on invalid data when submit stale is switched off) but he wont implement it since (according to him) it will not work with the code (i.e. he can't do it ) and his other excuse was that there will be a new firmware to resolve this real soon now ... (4-6 weeks?) ...

P.S. 'quit' quits cgminer ...