conflicting libraries at runtime

I know this is a bit off-topic, but I was hoping someone can point me in
the right direction. I've been spinning my wheels on this for a while now.

I'm having trouble with PL/R giving me a SIGSEGV *only* on Red Hat 9.
I've isolated it (at least the symptom) down to this: on RH9, a call to
re_compile_fastmap() uses /lib/tls/libc.so.6 instead of the
compiled-into-R function with the same name. The /lib/tls/libc.so.6
version of the function calls re_compile_fastmap_iter() which then
generates the SIGSEGV. I have tested a very simple standalone app, on
the same box, also linked to the same libR.so, and it uses R's builtin
re_compile_fastmap() (which has no re_compile_fastmap_iter() function).
The standalone app works fine. These calls happen during the early
initialization process of R.

R itself works fine and passes all of it's regression tests.

I've tested *exactly* the same PL/R code on RH8 and RH7.3 boxen with no
problems. gdb shows that on those machines the libR version of
re_compile_fastmap() is used, just like the standalone app on RH9.

Any ideas? I'd be happy to provide more info (off list) if anyone wants it.

Thanks,

Joe