We just upgraded to 2012, and discovered that if you pick an xref that has been xclipped, the xref is highlighted along with its xclip boundary, which appears with grips you can stretch to change the shape of the boundary.
I've noticed, however, that sometimes stretching these grips gives unexpected results. I have a drawing that contains a block composed of a clipped xref plus some lines and polylines. When I edit the block in the block editor and try to alter the xref's xclip boundary by stretching its grips, sometimes the grips cannot be moved to the intended destination. If I select the xref, then select one of the xclip boundary grips, move the cursor to a new location and click the mouse, the grip moves, but to a location far away from where I clicked. This is true whether or not I try to use osnaps to define the point I want.
If I try to move it again to where I want it, the grip moves further and further away, until finally AutoCAD complains that the resultant boundary would be self-intersecting and refuses to move the grip.
So far the only solution I've found for this is to revert to the pre-2012 method of invoking XCLIP, selecting the xref, then entering "P" to generate a polyline, editing the polyline as needed, and then using XCLIP again to re-clip the xref using the edited polyline.
Anyone else experience this, and/or know of a solution?