Thanks again for the suggestion. I tried calling support, but they say not until I buy a licensed version. I thought per incident support was available?
I've emailed sales to see if they can't provide some guidance; I called but nobody was there (it's Sunday; probably watching the Super Bowl). It seems from the website that per incident support is available:
But what do I know? I'd hate to buy and then be told tough luck -- you still have to buy the product. Not that buying is a bad thing, but as the product goes what I have with the free version works for my small business.
Anyway, for anyone industrious enough to review this thread I found a few more details that my be helpful. I did try taking the drive offline and mounting it to another LINUX box -- tried the open source drivers at: http://code.google.com/p/vmfs/ and also tried using vmfs-tools described here: http://planetvm.net/blog/?p=1592
..But no luck. The open source drivers were pretty cool as I could connect via ssh from one LINUX box to the ESXi box as follows:
user1@user1-virtual-machine:~/Downloads/vmfs_r95$ java -jar fvmfs.jar ssh://root:password@192.168.1.111/dev/disks/mpx.vmhba1:C0:T0:L0 info
Might come in handy with scripting backups and such down the road...
-- That worked against the vmfs partition that represents the good datastore, but didn't recognize the bad datastore as a valid vmfs partition. 
Neither did doing the same using those tools against the drive while mounte directly on another machine.
Something I did notice though -- I have another machine that is exactly the same; different VM's, but carved out and provisioned identically. I compared the output of fdisk -l and noted that the good machine against the disk in question had a FAT16 partition as well as the VMFS partition. (not sure if using the word "partition" in this case is accurate -- hope you understand my meaning). On the other machine with the drive in question I don't have a FAT16 partition. So maybe when I tried to rebuild the VMFS partition from one of the knowledge base notes (mentioned earlier in this thread) it grabbed a little too much? See below the good disk from one machine compared against the bad disk on the other machine:
Good Disk on Machine #1
~ # fdisk -l
Disk /dev/disks/mpx.vmhba1:C0:T1:L0: 750.0 GB, 750035927040 bytes
255 heads, 63 sectors/track, 91186 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/disks/mpx.vmhba1:C0:T1:L0p1 1 523 4193280 6 FAT16
Partition 1 does not end on cylinder boundary
/dev/disks/mpx.vmhba1:C0:T1:L0p2 523 91187 728263648+ fb VMFS
-----------------------------------------------------------------------------------------------------------------
Bad Disk on Machine #2 (note no FAT16)
~ # fdisk -l
Disk /dev/disks/mpx.vmhba1:C0:T1:L0: 750.0 GB, 750035927040 bytes
255 heads, 63 sectors/track, 91186 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/disks/mpx.vmhba1:C0:T1:L0p1 1 91186 732451481 fb VMFS
Thanks in advance for any light you may shed on this issue.