is the superuser app still there? what method did you use to root?
the stock rom will repalce cloclwork with the stock recovery on reboot. while youre still on a stock rom,you will have to flash clockwork EVERY time you want to boot into recovery.
in rom manager,go to settings andmake sure "erase recovery" is checked. flash the alternate recovery. then flash clockwork recovery again. if you still have root access and that works,you should be able to boot into recovery,make a backup,and flash the rom. while on a custom rom you wont have the triangle issue
the other possibility that comes to mind is that you used z4root,wich sometimes is "temporary". ive read about people having to use it a few times before the root "sticks".