I'm gonna defer to STaSh on this one, he could be right about the SP making the difference on those servers.
If you have another server around you could sacrifice for a 2k3 box, you can do DFS on Win2k3 Web Edition, which is only around $400 if you know where to get it

<nudge><nudge>
Thought don't think that Win2k3 solves all the problems, it's got some issues of it's own that caused us lots of problems and that won't be fixed until SP1.
Make sure that SP3 is installed, then try the stuff in the KB article that STaSh posted, but be sure to take note of this:
"Once the new value for the staging path has replicated to the domain controller that the FRS replica member is bound to, restart the FRS service. FRS on non-domain controllers favors domain controllers in the same Active Directory site. Domain controllers bind to themselves for configuration data."
You need to be sure to stop FRS on all the DCs and make the changes before you restart them or replication may possibly nullify your changes, that could also be what's blowing it up for you.
Is there any pattern with those three servers? All DCs, all not DCs, all without the SP, etc.? Try to find a common denominator.