Lewy,
As you have said that this happens in both table AND form view - I have experienced this weird behaviour.
I can't say that it IS a specific bug, but it does occur with MS Access, and, I can only put it down to 'memory' problems, and (through experience) specifically to 'graphics' memory problems.
Your only solid proof is to run this application on another machine.
If you can replicate it there - there can be no other conclusion than it's MS Access.
If not (which I believe you'll find) - then, it's this current machine, and then - look at updating graphics drivers specifically.
I doubt if you'll find any specific 'bug' report on this. It seems to be related to how MS Access or Windows handles memory / graphics and / or in conjunction with such applications as antivirus / malware etc.
Sorry - it's all very vague, but hope this helps you to pinpoint where YOUR problem lies for what is a very frustrating problem (believe me - I know it).
ATB,
Darrylle