[plt-scheme] strange module behavior

Hello,

I'm baffled at this problem: I am working on a medium-sized program at
work with about a dozen modules. I have a "util.ss" module with a bunch of
library functions, 35 in all. But now when I try and add a new function to
the module and then run the program (which requires other modules which in
turn require util.ss), I get:

dynamic-require: name is not provided: pairof by module:
|,c:\projects\myprogram\util|

I've checked and double-checked, and I absolutely do have the "pairof"
function in the (provide ...) clause of the util module. What's even more
bizarre is that if I remove some functions from the provide clause, the
program works, but if I remove others, I get this dynamic-require error
about the pairof function. I can't see any pattern here.

I know it's hard to track down the problem without code, but unfortunately
it's proprietary. Is there perhaps some common pitfall that I'm stumbling
into that folks know about, or could I be grappling with a MzScheme bug?

Thanks,
Dave Herman
dherman at ccs.neu.edu