Most annoying Auto "De-selection Bug" in XL

Having a most annoying bug in XL while connected to the internet. When we are running XL & internet at the same time a mysterious "De-selection Bug" sometimes appears. Basically, whatever cell is selected is automatically deselected after what appears to be a set period of time, which means I must Re-click the cell, sheet or reselect selected cells and all functions & macros are slowed down or lost (require debug) completely. The bug only appears while connected to the internet, no viruses or other unusual behavior have been detected. The only solution I have at the moment is to break the internet connection and then it stops, XL works normally.

Any help, comments, would be much appreciated.

Thanks

PM

no macro code but does seem to be worse in those notebooks, even workbooks that don't allow macros were effected today. Its okay at the moment, that is I'm online & not being "deselected" within XL. It doesn't occur all the time I'm online, that's what makes it so annoying and suspicious. I can't quite figure it out, whether its the ISP or certain web sites or something else.

Thanks but I still don't understand. Even if the focus is moved, excel deselects the active cell automatically so the problem is within excel?
Does anyone know how Excel would deselect? I can't do it manually.
If I can create the problem myself we might be able to fix or at least understand where it is coming from?