Layout XL 6.16 Very Slow Cell Manipulation

 I just started using 6.16 and everything has gone smoothly with Virtuoso Schematic XL, Layout XL, Spectre, Assura DRC/LVA. No real problems other than the nut behind the wheel. I'm not a system administrator, just a design engineer without any system support structure behind me.

 My issue is that I begand to construct an input differential pair with many stripes for low noise. This required an array of many smaller PMOS devices (.35um). As I built the diff pair from smaller clusters of devices (3 cells deep), everything went fine until I was connecting them at the top level. At this point, displaying the complete cell when viewing all layers isn't a problem, but if I grab one of the 4 sub cells to move it or otherwise manipultate it, the computer hangs for many minutes. In this case, the only thing that moves is the mouse cursor, but no new terminals can be brought up and nothing can be done until it clears. Not even RHEL6's "Top", which monitors system activity in near real time, will update until this issue clears.If I deselect visibility (CNTRL f), there is no problem; only viewing all the layers as in "shift f".

 My computer is a Dell M4600 workstation with 16GB RAM.

 I thought it might be the video card, but if I zoom in to a part of the cell that has very few polygons visible on the screen, select it and try to say, flip it horizonatally, the same thing happens.

Any ideas?

Thanks, Doug