thanks Adam a fair thought, I'm not seeing any other erratic behavior at all, takes pictures fine and you can view on screen for as long as you like, other functions that come up on the screen when viewing shots like filters, histogram, info etc all ok. just menus and the fn functions ISO etc. wont stay on screen most of the time, all the buttons seem to have a definitive tactile feel to them and all seem to preform their functions. It could be some leakage across a switch or control lines on a chip or PCB, but I'd have to open it all up to check that, just thought some one may have had the same issue.
Electronics with micro controllers in them
I can't count the times I've gone in search of hardware faults only to find later that its some undocumented software issue that magically disappears with a software update, or re initialization.