i don't get it

My lappy sweems to be having a personality split...

All started last weekend, when I turned it on to find...not my desktop picture(Tu/R). But the last one I had set...months and months ago (grass).

So I switched in a new and different pic (Queen Tu/R). Lovely.

Then the next time I turned it on, my desktop piccy was back (Tu/R)...but as I'd reset it to have the new one(Queen Tu/R)...that was weird. but I left it (Tu/R).

All last week it stayed ok. Now today when i turn it on...it's back to the new one I set (Queen Tu/R)!!

WTF is going on?

Anyone got any wise insights?