Video signal disappears and does not returns after reboor

Question

to improve security I added myself to all the groups that 'pi' had. After this precaution I changed to root and deleted 'pi' with deluser --remove-home However I got a warning about files left in 'pi' home directory. I rebooted and manually deleted the rest of 'pi' home directory. Then I continued installation in my name without any trouble. The system works fine, but after the usual 5 minutes timeut the screen becomes black. If I move mouse a bit or hit a key, I get back the picture. If I do not touch for ten minutes or so, the video signal does not come back. However I see torrent client running, ethernet trafic is running by l.e.d. If I join to raspberry by ssh and reboot it, the video signal is kept dead. Removing power and boot agaig, everything is ok - till the timeout. I could debug te raspberry via ssh, but I need help what service is die and how to repair it. Any debug advice is welcome.