Filleting producing z values

Forgive me if this has been answered somewhere else but its next to impossible to search for as I keep getting the old non-coplaner issues rather than what I'm looking for.

I'm having a problem at the moment on a particular drawing while filleting. If I draw two new lines in the world ucs so all start and end points have 0 z values. Then I apply a fillet to the two lines while still in world ucs. If I pick the arc the fillet command has produced and look at the properties, it has given the arc z values for the centre, start and end. Its only a small z value (0.9units) but it is throwing errors into the drawing everytime someone uses the fillet command.

Does anyone have any idea why this might be? I'm hoping this is a fixable problem as it is a large drawing and if the file has corruption problems its going to involve a lot of work!

I had similar issues with Xref & snapping onto them rather than keeping on a level '0' Z value.

If you go into the options, under drafting you will see in the bottom left hand corner tick boxes with options regarding 'Z' value - try playing with about with these.

Will the command flatten work? * hang on, not what I thought.....

Its the flatten lisp your after - the command has stalled my CAD!

I think there's a few lisp routines on here under non coplanar & fillet help, if you do another search

Yeah I've got a couple of flatten lisps already. I'm using them as a stop gap at the moment but I really want to stop the problem happening in the first place.

Since I 1st posted I've done a bit more scouting around, if I get the user with the problem to run through the commands I described before he gets the z error happening. If I do it on my machine it seems to work as it should with no z values created. Oh and the user only gets the errors on this one drawing, if I open a new blank metric template and get him to do the same thing it works fine!

The only difference between the drafting set up on the two machines is I'm running 2010 and the user with the problem is running 2009 LT. I know LT can be a bit temperamental but I've not had it failing with very basic drawing tasks before!

Its bizzare!