My first post and from a non-techie, so please excuse misdescription.

I have a Nexus S running on Android 4.0.4. I have had it for several months and am very pleased with it.

For the last 24 hours it has a text overlay on all views in the top right hand corner (the device and all applications otherwise seem to run as normal, but the text overlay partially obscures part of the screen).

The text varies - on home screen with no apps running it reads (for instance):
"1.21/1.23/1.13
system_server
com.android.systemui
kworker/0.0"

The number of lines and the text varies and there are more lines when applications are being run or opened.

I have searched everywhere I can think online with no joy....reboot does not help.

Any advice gratefully received....