'apt-get update' crashes

[Nathan Weston <elbows@spamcop.net>]

I have both stable and unstable in my sources.list, for and for about the last 
week, apt-get update keeps failing with the following error:

Reading Package Lists... Error!
E: Dynamic MMap ran out of room
E: Error occured while processing lyx (NewVersion1)
E: Problem with MergeList /var/lib/dpkg/status
E: The package lists or status file could not be parsed or opened.

If I comment out the lines for stable, or the lines for unstable, everything 
works fine.
My first thought was that this was the result of some bad file being uploaded 
to unstable, but since the problem has persisted I have to assume this isn't 
happening everyone.

This is the sources.list that causes the crash:

#Stable
deb http://ftp.us.debian.org/debian/ stable main non-free contrib
deb http://non-us.debian.org/debian-non-US stable/non-US main contrib non-free

#Unstable
deb http://ftp.us.debian.org/debian/ unstable main non-free contrib
deb http://non-us.debian.org/debian-non-US unstable/non-US main contrib 
non-free

Thanks in advance,
Nathan