Share your experience!
Here's one for you:
My lock screen usually looks like this:
But on occasion looks like this:
Any ideas? 
this seem`s like an software erorr ,but my gues is hardware problem ,try to repair software with pc companion/seus,if after the repair the problem appear again go to service/sony service repair
I do suggest using the information provided above, here is a link to PC Companion,
Well I've noticed this both on the UK .67 generic s/w and a clean install of Sweden .75 generic s/w.
It doesn't really bother me that much and only happens very rarely, I was more interested to see if others had noticed this - it looks like a s/w bug to me.