mock builds failing under CentOS 4.4 host

[Jeff Sheltren]

I'm not sure if it was the move to CentOS 4.4 or what, but now my  
mock builds are failing on CentOS 4.4 hosts where they were working  
fine a couple weeks ago...

Digging through root.log shows this message buried in the middle of  
all the 'yum install' output:
error: can't create transaction lock on /var/lib/mock/fedora-4-i386- 
core/root/var/lock/rpm/transaction

So far, I've had similar results building for FC3/FC4/EL4, so I'm  
guessing its a host machine issue rather than a chroot issue.  Has  
anyone else come across this already?  I am using an older version of  
mock - 0.4-2 on one machine, and 0.4-5 on another; has something  
changed since then to fix this issue?  I guess I need to upgrade  
eventually to get the newer mock config setup, etc. but I've been  
putting that off...

Thanks,
Jeff