Recent problem with security repository?

[Benedikt Hallinger <b.hallinger@ergonaz.net>]

Good morning,
at one of my boxes i run apticron. Since the last night, i am unable to use
aptitude (also apt doesn't work) anymore.

My sources-list contains:
deb http://security.debian.org etch/updates main

This happens if i do an aptitude update:
Hit http://security.debian.org etch/updates/main Packages
Fetched 4B in 0s (5B/s)
Reading package lists... Error!
E: Dynamic MMap ran out of room
E: Error occurred while processing libcairo-directfb2 (NewVersion1)
E: Problem with MergeList
/var/lib/apt/lists/security.debian.org_dists_etch_updates_main_binary-amd64_Packages
E: The package lists or status file could not be parsed or opened.
E: Couldn't rebuild package cache

The errors do also occur if i run any other apt/aptitude command.

Strangely, on my other box this doesn't happen. Is something corrupt on the
machine?
If i manually remove the package cache and do "aptitude update", the
problem is reproducable.

Any help is greatly appreciated.
Thank you,
Beni