Pipework Problem. ACAD MEP 2009

I'm currently using ACAD MEP2009, and drawing some 3D pipework runs. The problem i'm having just started recently,

I open a drawing with some existing pipework in it, and when i try to add to existing runs, or even draw some new. The program starts the command but the automatically cancels it. So i'm basically unable to draw anything 3D. All the 2D functions work correctly. I have tried all the obvious quick fixes but to no avail.

Also another litte quirk is that when i unload and then reload my profile, a command will work once but then revert back to the above problem.

If anyone has experienced this before or has a solution, i would be grateful to hear from you.

Thanks in advance.