Have you tried using a different media.pk2?
Because most files of data.pk2 are related to media.pk2 entries.
Maybe you added the wrong entry somewhere in your media.pk2 and the .bms gets loaded wrong?
If that is not the problem then the entry might also be in any other .pk2 (if you modded anything else)
If it's not that you might also ensure that it's the client by using a totally different one.
Also if it stops at 238mb ram usage it's close to the point before the client actually opens, do you use any alexandria intro? Did you add custom objects to the intro?
Sorry but I can only guess here, hope I could help anyway