[Dridzt]

Your OnEvent is a couple parameters short too:
xml

<OnEvent>GuildLevelUp.OnEvent(self, event, ...);</OnEvent>

lua

function GuildLevelUp.OnEvent(self, event, ...)

Secondly it looks like the script handler in the xml are trying to call functions that are out of scope.

You have 'local GuildLevelUp' on top of your .lua file.

Try changing the function names in the .xml to GLUA.OnEvent and GLUA.OnLoad
The whole getting a local reference to a global table deal is pointless for this particular case btw.