Look at the add ins, in tools add ins. Do you have many activated? What happens when you restart SW? I might guess that your add in is messed up. How many processes are running for this add in?
I have a point sometimes where my toolbars go haywire and I have to turn to my saved SW registry file. When was the last time you started a new swsettings.sldreg?
So it appears that the Autodesk Simulation Mechanical addin was causing the problem. I always use the standalone Autodesk Mechanical application anyway, so I just disabled the addin in Solidworks via the tools > addins menu. Disabling the addin seems to have fixed the problem with no blank tabs opening up now. Thanks for your help,
I've heard people say that they rename their registry file as 'old' when things go haywire and let the computer automatically create a new one. Are you saying that you do it in reverse Steve? Do you keep a copy of a good registry file and just reinstate that when things go crazy?