I am running Autocad 2011 on a reasonably high spec Toshiba and also have a Dell with the same software loaded.  I have a 3D drawing with 4 panes.  I have saved it in dxf format, but when I try to reload it I get the error message:Error in VPORT Table

Invalid symbol table record name:*Multiple on line 1768.

Invalid or incomplete DXF input -- drawing discarded.However, if I load the dwg version of the same drawing it opens without problems.  I have then re-saved from dwg to dxf, but every time the dxf gives the same error message.I then copied the dwg to my Dell and tried converting to dxf again, but got the same error message on the dxf version.Other dxf drawings in 2D and with no panes open without problem.It cannot be a corrupted programme as there is the same error on both computers, both of which have worked well in the past.Does anyone have any suggestions how to overcome this problem.  I need dxf as our laser cutter will only accept files in this format. The files are too large to upload to this forum (16MB and 3MB).  My one thought is that the file size is too big, as only part of the file converts to .stl - saying the history file is too large.  Is there any way to reduce this - apart from using BREP, which I believe makes the drawing un-modifiable.Thanks,Art