I was trying (once again...) to get something done with my CD-RW writer, and in the process created a directory I didn't want, "/cdrom2" which I then deleted using rmdir.

Fine and dandy. The only thing is, somehow bash became convinced "cdrom2" was its present working directory, and every time I opened an xterm or su'd inside one, I would get a two-line error message about being unable to find the parent directory, the current working directory not existing, etc.

Finally I got tired of this (though it was just an annoyance and didn't hurt anything) and rebooted and now I'm back to "normal."

Question: Was there a way I could have convinced bash without rebooting to use another, existing, directory as its "present" working directory?

I searched here and on Google and could not find this problem!

The process from which of all the commands you issued was in the
directory /cdrom2 when you deleted the directory, I'm
betting.

Almost every time you issue a command, it execs (creates another
process to run the command). This means the new command
can't find it's cwd. It inherits that from the parent. It had nothing
to inherit.

Next time, try:
cd <- puts you in your home directory
or
cd / <- puts you in root directory

then issue
rm -R -f /cdrom2 to delete the directory and it's contents and subdirectories

That may be what happened, though I thought I'd moved up a rung in the hierarchy to do my rmdir. Actually I thought it was impossible to remove a directory while you were still in it, but that could just be a remnant of my Windows days coming back to haunt me...

Next time, I'll be extra careful where I am when I use rmdir command! Thanks for the suggestion.