Just use the backup application from the N900, enter a name (for example backup 27.05.2010) and tick everything.

Then connect your phone by USB mass storage on your PC and navigate to the backup folder. You should see a folder named "backup 27.05.2010" as your backup name and there are some *.zip files into it.
The comm_and_cal.zip file contains this line /home/user/.rtcom-eventlogger/el.db quoted by ossipena

You can copy the entire folder to your pc to be safe.