Problem Fixed:
I performed the following on the problem machine and the problem was fixed:
1. Open AutoCAD Map3D 2012
2. Left Click on Layout1 to select it. (Or any other layout)
3. Right Click on Layout1 and choose "Plot..."
4. Under "Printer/Plotter Name", choose "Default Windows System Printer.pc3". It took about 30-40 seconds to select the printer. (In comparison to selecting the others which was right away)
5. The printer was not selected, it just showed a blank selection.
6. Click on Cancel to close the "Plot..." window
7. Right Click on Layout1 and choose "Plot..." again.
8. Under "Printer/Plotter Name", choose "Default Windows System Printer.pc3" again. Again it took about 30-40 seconds to select the printer.
9. This time "Default Windows System Printer.pc3" stayed selected. Click the "Ok" button.
10. Close autocad, open autocad, and now do a netload, run your dll, run your commands etc., as usual...
Problem was gone!