This happened to me twice the other day. I switched on the SL with the Vario-Elmarit. No picture could be seen on the screen but there was the virtual horizon moving and the information around the screen including aperture and time, if accurate i do not know.
For Sweden it was a nice warm day, 23°C. The camera had been lying in the boot of my ACed car. Switching of, removing the battery did not help until eventually. In a while the fault was repeated. Now the LS seems to be working fine again.
This failure I think was due to heated sensor.
Have you who use the LS in warmer surroundings had this problem?
/Eric