Elbox 1240 & artefacts on the screen

[Doobrey]

It could be timing issues that are known to occur on some A1200 revisions when using an 040/060 processor.

If you're handy with a soldering iron have a look at Ian Stedmans page on A1200 modifications

Edit..
Although after looking at the pic again, it doesn't look like timing problems, Are you running any patches/improvements at startup?

[Doobrey]

Have you tried removing any memory on the 1240 to see if the error goes away?
BTW, Is the 1200 still being powered from its original PSU? And do you know what revision motherboard it is (printed next to the expansion connector, it'll say something like  Rev2B or Rev 1D4)