I had the same problem with Parallels freezing my Mac hard (no kernel panics) with the latest version.
I did some digging and I noticed the same thing in the system log:
Code:
Sep 19 21:43:26 Quad kernel[0]: Parallels Workstation Hypervisor started.
Sep 19 21:43:26 Quad kernel[0]: com_parallels_kext_Pvsvnic: Ethernet address 00:01:23:45:67:89
Sep 19 21:43:29 Quad SystemStarter[73]: Parallels VirtualMachine drivers (138) did not complete successfully
Sep 19 21:43:29 Quad configd[64]: target=enable-network: disabled
Sep 19 21:43:30 Quad SystemStarter[73]: The following StartupItems failed to properly start:
Sep 19 21:43:30 Quad SystemStarter[73]: /Library/StartupItems/Parallels
Sep 19 21:43:30 Quad SystemStarter[73]: - execution of Startup script failed
Sep 19 21:47:38 Quad kernel[0]: Parallels Workstation Hypervisor exited.
Sep 19 21:47:42 Quad kernel[0]: Parallels Workstation Hypervisor started.
Sep 19 21:47:43 Quad kernel[0]: com_parallels_kext_Pvsvnic: Ethernet address 00:01:23:45:67:89
Sep 19 21:47:46 Quad mDNSResponder: Repeated transitions for interface en3 (FE80:0000:0000:0000:0201:23FF:FE45:6789); delaying packets by 5 seconds
Sep 19 21:48:02 Quad mDNSResponder: Repeated transitions for interface en3 (10.37.129.2); delaying packets by 5 seconds
after some digging in the StartupItem I noticed this line:
Code:
# as well as Cisco VPN client
/System/Library/StartupItems/CiscoVPN/CiscoVPN restart
after commenting that last line out, since I do not have the CiscoVPN software installed, I now only get these syslog entries upon startup of the Mac:
Code:
Sep 19 22:02:24 Quad kernel[0]: Parallels Workstation Hypervisor started.
Sep 19 22:02:25 Quad kernel[0]: com_parallels_kext_Pvsvnic: Ethernet address 00:01:23:45:67:89
Sep 19 22:02:27 Quad bootpd[214]: interface en1: ip 192.168.99.211 mask 255.255.255.0
Sep 19 22:02:27 Quad bootpd[214]: interface en3: ip 192.168.2.1 mask 255.255.255.0
and so far, no freezes... Of course this could just be a coincidence, but hey, it works 
Commenting out the line should not be Parallel's solution of course, maybe test for existence of /System/Library/StartupItems/CiscoVPN/CiscoVPN before trying to start it?
But I have had no luck getting VT-x enabled by putting my MacPro to sleep... (update: well, it has just worked for the first time...)