So strangely I have also started to get these messages. Also for E-mail and occasionally for Phone. I can't start most of my applications except some core maemo ones (media player, calendar, contacts etc. E-mail crashes as soon as I open some mail folder. Web does not start at all. As also Open Media player, Marble, gps-recorder, StellariuMobile etc. I'm at cssu-testing + cssu-devel + kernel power 52.
The last thing I installed was a new libpng from cssu-devel but after that the phone worked OK.
The last thing I did before it happened, was for testing kp52:
stop bme
modprobe bq27x00_battery
modprobe bq2415x_charger
The battery still showed o%, so I started bme again and the phone rebooted.
After reboot these messages ("Internal error. Application 'Web' closed") started to appear...
I do not think it is strictly related to cssu-testing though...
Any ideas besides reflash...
And yes, I searched talk.maemo.org forums on that problem before posting