Pardon me if this is a stupid question, but what do you mean by, "This is probably unfixable"--the specific problem you were trying to fix, or the whole epic spellcasting situation? (I'm pretty sure I have successfully cast epic spells as a PRC class character before. Yeah, I used Dread Necro-Cleric-True Necro and cast epic spells. I think I also used to cast epic spells as a Sublime Chord.)
Edit: Okay, that was a stupid question. I figured out the unfixable part must be the server player's problem, not epic spellcasting in general. The question below is still valid, though.
And is the problem from the server player something we should be aware of in general, like certain character builds that just won't ever work? (I always like to know this kind of thing before investing a lot of time in a build.)