If you load code or debug, you get one use then the ST-Link appears to lock up, then the ST-Link must be disconnected and reconnected, then you get one more use. Repeat until you are ready to scream.
This is a point of discussion in the openOCD forums as well as libUSB forums. Nobody can put their fingers on what the issue is exactly, everybody keeps saying that it is not their fault, but there is one thing that keeps coming up.
The serial numbers in the ST-Link modules, whether standalone, or built onto Discovery or Nucleo boards, are numbers like:
instead of the more normal:
CC2D630GKJDGFKL0 or 42
Nobody knows if the problem is ST's use of unprintables in the serial numbers, but if that can be fixed we can rule it out and move forward. If I can get some help from ST, I'd be glad to bootload some firmware into my ST-Link to get over this and help out a whole bunch of people.
Please ST, you're our only hope.