Yeah, it was pretty odd to be honest. Now that I think about it, the error could have been due to GB. I had selected "Back-up current ROM" and to my knowledge the error took place right as the phone entered Recovery. It did ask for me to reboot and re-start ROM Manager so that an error report could be submitted. I did so, I don't recall then the data being populated into the e-mail.
Whatever the "latest" version was as of 2:00PM EST yesterday was what I was running, 5.0.1.0?
Just flashed the 9/02 nightly (the one labeled incorrectly as 9/03) from ROM Manager and it worked fine...whatever may have happened before doesn't appear to be due to a defect that I can find in ROM Manager. I even included a backup of my existing ROM to make it a more complex action. I've also used the install ROM from SD card option several times over the past few days w/out issue.
I would say that unless we have additional input that there is a problem, that flashing ROMs using the Install ROM from SD Card option or the Download ROM option (to get Gapps) from ROM Manager works...