1) Power TV down fully (disconnect from mains) and leave it a few minutes.
2) Unplug the stand from the TV
3) Keep the stand unplugged, and power up the TV.
4) Reset TV to factory default via the service menu.
5) Power the TV down (disconnect from mains) and leave it a few minutes.
6) Reconnect the stand whilst the TV is still powered down.
7) Power up the TV and reconfigure. It should work ok now if it's a software issue.
8) If it doesn't work, repeat steps 1-7 a few times. Sometimes it takes a few tries...
If that doesn't work, there's a chance you've inadvertently unplugged and re-plugged the stand with the TV powered up (even if it means the DIN plug has moved a millimetre out and in again, it all counts as a plug/unplug). This can short out the module which controls the stand and damage it. It's a cheap little module... which unfortunately is part of the main chassis - and this means a new chassis at hundreds of pounds / Euros / Dollars.
7 times out of 10 it's steps 1-7. Good Luck :)
Lee