Sometimes can't reselect objects

Hello,

I'm using Map 3D 2005 and I noticed a strange bug when using some drawing files. I can select or grip an object to see it's properties or modify it etc but after I finish sometimes I can't reselect it the same way. For example:

In model space I select a line with a crossing (or solid) box. It's grips are displayed and I grab one end to stretch the line. I then clear the grip with the esc key and sometimes when I try to repeat the process the crossing box does not pickup the line. The only way I can select it is by issuing a command like stretch or list etc. When I can't reselect I can fix it temporarily by saving the drawing. Once saved I can then reselect the object by using a crossing box. But after I do it once it usually prevents me from reselecting again and I have to repeat the process.

This gets annoying since I frequently try to select and reselect objects to see what layer they are on, to move blocks or stretch objects. Any tips on what settings I should check? I posted in the autodesk forum last week but had no replies.

Thanks.