It could possibly be a lack of memory problem... try closing down as much of the programs on your computer that you can before running sims, the other possibilty is that you have downloads that are conflicting and can often cause things to flash various shades of blue. If this is the case you'll have to find out which downloads are causing the problem. There are some programs that look for conflicts but can't remember the name of them at the moment.
Hope this helps.