Same problem here.
All the same symptoms, except the hanging on shutdown.
And with me it only happens when connected by wifi. No problems on ethernet.
At a fresh boot of the computer all the shares are accessible through there assigned driveletters.
When I close my laptop so it goes into sleepmode and then reactivate it (no matter how short or long I wait in-between, seconds or days doesn't matter), I can no longer reach my shares.
a Reboot solves this.
For quite some time I blamed Win 7 because I did not have this problem on XP, and it started when I made the move to Win 7.
But now it appears that if I change Trusted Zone Security from "Medium" into "Off" I have no problems anymore.
So it's obviously ZoneAlarm.
Hope this gets fixed soon.
Computer : Dell inspiron 6400 & Dell inspiron 1721
OS : Windows 7 Home Premium
ZoneAlarm : 9.2.057.000 Free