Okay - methinks I have this solved. It appears that the initramfs was bjorked and needed to be rebuilt. In case anyone else is unfortunate enough to have this happen to them when upgrading a Red Hat 6 guest from workstation 9 to 10, here's what I did to fix it:
1 - In the settings, have the CD/DVD device point to the original RedHat iso installation image file. Of course you could probably use some other pre-made rescue disk, but alas I didn't have one.
2 - Right click the VM (if you have the Library pane active) and under the Power menu for that VM, select "Power on to BIOS". It should come up in the PhoenixBIOS Setup Utility screen.
3 - While in the BIOS, using the right arrow button move over to the Boot section.
4 - Use the arrow key to select CD-ROM Drive, and tap the + key until it moves to the top.
5 - Tap the right arrow key to Exit, select Exit Saving Changes and hit enter, select Yes to save and exit, and the VM will boot to your .iso image.
6 - Select Rescue installed system.
7 - Step through the options for language, etc., and when it asks What type of media contains the rescue image? select local CD/DVD. Allow it to start the network as well.
8 - Select Continue on the next screen to actually mount your original system image. If you select Read-Only you will not be able to edit anything. This is good later if you just want to poke around and look.
9 - It says something like your system has been mounted under /mnt/sysimage , so just keep hitting Ok until it asks you to start the shell. Select shell and hit Ok.
10 - At the bash prompt type chroot /mnt/sysimage
11 - following the instructions here http://advancelinux.blogspot.com/2013/06/how-to-rebuild-initrd-or-initramfs-in.html I rebuilt the initramfs file for my version of Red Hat. To paraphrase that site, I executed the following commands:
First made a backup of the existing initramfs file (ha! as if it would boot anyway!)
# cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.bak
Made the new initramfs file:
# dracut -f
Keep in mind that if you are in a kernel version different to the initrd/initramfs you need to build, (such as if you are in Rescue Mode where you booted something other than the stock kernel version) you have to specify the full kernel version, including architecture. Mine is below:
# dracut -f initramfs-2.6.32-279.el6.x86_64 2.6.32-279.el6.x86_64
After the new initramfs is built, reboot the machine and with luck it will boot up just fine.
Thanks to Darius on how to capture the boot log to a file on starting up a Linux VM. That was very helpful! When I created the Serial device on my machine though, it popped up as serial1 when I looked at the vmdk file for this VM configuration. So the kernel line in my grub.conf file after removing "quiet" is "earlyprintk=serial1,keep". I had to look deeper at it because when I initially changed that line to use "serial,keep" I was getting nothing in the log file.
Thanks all!
Ryan Hulslander