drive disappears from WExplorer

I've got a bigger problem, but in working it I come up against a sub-problem that I'd like to figure out.

I'm running W7 SP1 and I've got a drive that I can see. Then, s... happens and it's gone. It's still on the network because I can see it from other devices, but not from my PC.

If I reboot, there it is again.

Q: Is there any way I can re-see this drive without rebooting?