Make sure your antivirus has the very latest definition updates - this is not a new problem with game guard from what I read. I seriously doubt you can play without this file intact, and I also doubt that the file itself is infected with anything if you got it from a reputable download source.
Game guard can LOOK like a trojan to AV software as it intercepts program calls, updates itself so firewalls can block it as well, etc. It is not uncommon these days in mmo software so I wouldn't get my undies in a twist over it.
Norton Antivirus corporate edition with the latest updates did not find it a problem here.
You could try this.
1) Most AV software will quarantine suspect files. If you have the option to find it in the AV software you may be able to restore it and tell the AV software to ignore that file.
2) You could look for a setting in your AV software for what action to take when it finds an infection. If you change the default action from DELETE to PROMPT, when you reinstall Shaiya it "should" then ask you what to do with Gameguard.des, rather than instantly delete it.
3) Go to your AV software home page and try searching for gameguard and see what they have to say about it.
Good luck - let us know how you get on.
A link to the gameguard product page http://eng.nprotect.com/nprotect_gameguard.htm