apt-get update error

[Deboo <deboo@debian.elitemail.org>]

I'm using debian woody. After reading an article in LG on apt (Issue 86 -
Debian APT, part2), I wanted to try using some package from testing and I
did as per the artile, putting 2 new lines for testing and unstable in
sources.list. But after I apt-get update, at the end, I get this output:

Reading Package Lists... Error!
E: Dynamic MMap ran out of room
E: Dynamic MMap ran out of room
E: Error occured while processing magnus (NewVersion1)
E: Problem with MergeList
/var/lib/apt/lists/ftp.iitm.ac.in_debian_dists_stable_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.

I tried deleting this file and re-running apt-get update but still the
same. What am I doing wrong? The file seems to be fine if I open it with a
E: Error occured while processing magnus (NewVersion1)
E: Problem with MergeList
/var/lib/apt/lists/ftp.iitm.ac.in_debian_dists_stable_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.

I tried deleting this file and re-running apt-get update but still the
same. What am I doing wrong? The file seems to be fine if I open it with a
pager/editor.

Regards,
Deboo