My bad...poor choice of wording on my part.
I deleted these two files from my eq2map directory:
- icons_ obelisk_of_lostsouls_4.xml (timestamped August 24, 2005)
- icons_.xml (October 5, 2005)
I'm not sure where those files came from or why they didn't cause a problem until recently, but they're gone now and everything seems to be working perfectly again!