I've run into a similar problem, see attached. P8 Z68-v/GEN3 ASUS MB, 32GIG, also running an i7-2600. esxi 5.0.0 (Build 469512) is running on local ATA, and the data stores are on an Apaptec 5404 RAID 10. This is a new build, running 3 VMs.
This has happened on 3 of 6 nights, it seems when there is low traffic. The purple screens are all similar to the attached, but different PCPU affected.
2012-05-14T10:13:11.811Z [2B6C8B90 info 'ha-eventmgr'] Event 129 : Issue detected on vmlocal.stsolo.com in ha-datacenter: Heartbeat: 618: PCPU 6 didn't have a heartbeat for 8 seconds. *may* be locked up
2012-05-14T10:27:22.808Z [2B687B90 info 'ha-eventmgr'] Event 154 : Issue detected on vmlocal.stsolo.com in ha-datacenter: Heartbeat: 618: PCPU 4 didn't have a heartbeat for 8 seconds. *may* be locked up
2012-05-14T19:27:01.723Z [FFADDA90 info 'ha-eventmgr'] Event 191 : Issue detected on vmlocal.stsolo.com in ha-datacenter: Heartbeat: 618: PCPU 4 didn't have a heartbeat for 8 seconds. *may* be locked up
2012-05-18T23:37:22.928Z [FF911A90 info 'ha-eventmgr'] Event 49 : Issue detected on vmlocal.stsolo.com in ha-datacenter: Heartbeat: 618: PCPU 0 didn't have a heartbeat for 8 seconds. *may* be locked up
2012-05-19T02:43:26.927Z [FFF03B90 info 'ha-eventmgr'] Event 51 : Issue detected on vmlocal.stsolo.com in ha-datacenter: Heartbeat: 618: PCPU 6 didn't have a heartbeat for 8 seconds. *may* be locked up
In my case, unlike in ehinkle's, it lists "vmware.driveAPI" in the first stack trace.
I'm having trouble figuring out what is up here. I have a couple of other esxi 4 machines running similar hardware without issue.