[ThatOneGuy]

Typically, from my experience, crashing clients tends to be a problem with bad materials/textures in the server or not being precached or downloaded. If it happens when you are shooting, do you have bullet tracers going that use materials? If so, perhaps some clients have them downloaded and others dont. Either way, look into anything using materials/skins/models/etc. Your culprit will most likely be one of those, I believe. Good luck!

P.S. Save your money...no need to pay someone for advice on a common problem.