mock/yum problems with EL-5?

[Tim Jackson <lists timj co uk>]

Today I tried to do a "make mockbuild" in awstats/EL-5 on F-9 (with some 
local changes). I got the usual:

...
State Changed: lock buildroot
State Changed: clean
State Changed: init
State Changed: lock buildroot
INFO: enabled root cache
State Changed: unpacking root cache
INFO: enabled yum cache
State Changed: cleaning yum metadata
State Changed: running yum

and then yum seems to get into an infinite loop where it eats all my RAM, 
my system starts furiously thrashing and grinds to a halt.

I've never seen this before with mock/yum and I haven't changed anything 
about my mock config. Any ideas about what might be causing it? Anyone 
else seen a similar thing?

Thanks

Tim