R-11 Crash
This particular "Unmapped pages" error is likely caused by a conflict
in the way memory is split between expanded and extended memory, such
that AutoCAD wanders into memory intended for other uses. You should
check how your expanded memory is configured, and I hope you use QEMM.
If you post the contents of your Autoexec.bat and Config.sys files we
could help you out. Smaller drawings might not push you into the
same memory areas. BTW, 25M free space is not sufficient to load in
a DXF file of that size. Figure that you might need almost as much
space for the resulting DWG file, and about 2-5 times that amount for
AutoCAD's temp files and page swapping space.