[Samsung Epic 4G Touch] Darkendes:
Ok, here we go.

Coming from 8-3/CWM.RC10, I made a backup of my fully functional setup. I'll call it "8.3Backup".

-Went to recovery and flashed MergeMe without wiping anything.

-Rebooted and my Google account had been lost. If I go into Accounts and Sync, it only shows my Skype account and my email account (set up via email app). My Google accounts (two of them) disappeared. I couldn't open the Play Store (instant app crash, no error message) or load my calendar data.

-I went back into MergeMe's recovery and tried to make a backup. It rebooted halfway through with no backup made. This is the last_log for that.

-After that, I went back into MergeMe's recovery and tried to restore 8.3Backup. It got halfway through and rebooted during the data phase. I was back to 8/3 w/RC10 recovery, and my wallpaper hadn't changed, but I lost all my other data in the botched restore (apps, contacts, etc) and it sent me back through the first-boot setup and tutorials. Here is the last_log for that restore. I tried both ES File Explorer and Astro and neither would let me get to /cache. ES crashed as soon as I tried to open the app, and Astro said the directory was empty. I finally got the log from a different root file explorer.

-I went back into RC10's recovery and tried to wipe everything and flash a clean MergeMe. It got all the way to the boot animation and froze at the end, right before the lock screen loads. It did this twice before I had to manually reboot into recovery. CWM6.0.1.1 loaded with text at the bottom that it couldn't open /cache/recovery/log and /cache/recovery/last_log.

-I flashed RC10 again to see if MergeMe would boot with that kernel. Boot animation took forever and never booted... it didn't freeze, but never got past the boot animation. I waited 10 minutes. I was never able to get those logs.

-Hard boot into recovery on RC10. Restored 8.3Backup. Everything restored just fine.

I'm going to try out hammertime or whatever is newest tomorrow if I have more time. Hope this helps.

EDIT: Got some more free time so I decided to play around some more...

-After restoring 8.3Backup above, I wiped cache and dalvik, then flashed hammertime. So far so good. I haven't tested anything in depth, but my accounts are there and my calendar data loaded, which is further than I got with MergeMe. More to come.

EDIT 2:

-I tried to restore 8.3Backup from hammertime's recovery and it failed halfway through the data restore process again.

EDIT 3:

-I wiped everything and tried a clean install of hammertime. This is the log for that flash. last_log No errors flashing.

-I tried to make a backup. It failed again the same as before. Rebooted halfway through without much in the way of log data.

EDIT 4:

Interesting... I flashed RC10 on top of the same installation of hammertime as before just to see if that would change anything, and this time it worked. The backup went through successfully. That means it has to be something with the newer kernels, right? RC12 wouldn't backup for me when I tried it on nightly 8/6 so maybe whatever changed between rc10 and rc12 may be worth looking into? Maybe something with CWM 1.0.1.1 even? RC10 was CWM 1.0.1.0. Here's my log: http://pastebin.com/cT4V65YH

I hope this helps. At least now we know we can flash an old kernel and make a backup with the new builds.

Can anybody else having trouble making backups test this out?