Its been sometime since I did this but as I recall:
The tacks are stored in two places. One in a mysql table that actually propogates the xml file. I either edited the table directly in phpmyadmin or went to the settingsin admincp for this mod and found the user that had posted the link and removed it that way. It seems like there was a moderate users option or something for it, that had a list of all the users there location and comment data. Wherever that was, I deleted the info causing the the information that was causing the error in the xml from the database. And my own info from the database. Then I deleted the markers .xml completely, and I readded myself from the web interface, the modified database table re generated a correct xml file and it worked.
This was about 6 months ago so I can't remember entirely