Upgrading mysql on Ubuntu Lucid Lynx (10.04) hangs

Already the third time this happens to me: An update is available for the mysql server and I just "apt-get upgrade". The upgrade process gets totally stuck at the following task:
Preparing to replace mysql-server-5.1 5.1.66-0ubuntu0.10.04.1 (using .../mysql-server-5.1_5.1.66-0ubuntu0.10.04.2_i386.deb) ...
mysql stop/waiting
The process that got again stuck in some eternal loop (or whatever) is an egrep replacement of some textfile:
egrep -qi -r ^[^#]*ndb.connectstring|^[:space:]*\[[:space:]*ndb_mgmd /etc/mysql/
I just killed that process and the upgrade resumes as nothing would have happened.