I replaced the 64 MB CF Card in our 2821 router with a 256 MB CF Card. First of all, I had a heck of a time finding a 256 MB CF Card, which is the largest card you can put in this box. Anyway, after I transfered the files from my 64 MB card to the 256 MB card, everything booted fine, but now I can't access SDM or CCME admin page! I have no problems with Unity Express admin pages, though. I haven't had time to troubleshoot it, but I really don't know where to start, or what's cause it. I can still use the IOS command line to configure, but I sure miss using the web interface. Gotta fix this soon.
Found the problem. The files were not named with matching case. Since IOS seems to be a type of Unix variety, all the file names are case sensitive. Once I fixed that, all the web admin files worked again.