the updater SHOULD do an md5 check on the map files, but unfortunately it DOESNT, i noticed that i introduced a bug that causes the updater to only check if a file exists if it goes into the images/maps/ folder on the client machine, so it isnt checking it other than if its there or not. i already fixed the bug in the version i am working on, and there should be a short post about the bug on the firum, as well as the most recent thing posted in the "news" window of the updater itself.
about the only help i can offer is to try downloading the file manually, from here ->
http://maps.eq2interface.com/POI_fil..._lavastorm.dds
and then putting that file into the images/maps/ folder of your custom ui directory. i wish i could offer more help but it is extremely difficult find what causes the error or how to correct it when i can't ever get the the error myself.