I haven't been able to successfully flash ClockworkMod Recovery (which I LOVE) for days now, ever since the v2.5.0.1 recovery update came out. I tried flashing back and forth between alternate recoveries over and over again, and flashing the same Clockwork recovery several times, tried all of the other Clockwork recoveries (again, multiple times). What I've discovered through all of this is that if the recovery takes a long time to flash, then it's not successful. I was finally able to get A recovery by flashing SPRecovery successive times. I have to say that, while I was utterly grateful for having a recovery of any kind again, it really reaffirmed why I hate using SPR compared to Clockwork, since I tried out a number of new kernels while using it and had to rename each of them to update.zip and move them to the root of my SD card each time -- wow, what a pain!
What FINALLY worked for me today was running Pete's fix permissions update.zip (which I'm not recommending unless you're on BB) using SPRecovery, then uninstalling and reinstalling ROM Manager. Then, I flashed the latest version of ClockworkMod (2.5.0.1) once and it took a really long time, then immediately again and it flashed very quickly. Lo and behold, I'm in Clockwork recovery right now, getting ready to run a new backup. Woot!!
I won't be updating ClockworkMod recovery again any time soon.