AutoCAD 2010 :: Sheet Set Not Saving Settings

I am having an issue with my Sheet Sets keeping the settings I have entered after closing them out.

For example, I create a new Sheet Set (from Existing Drawings) add my layouts to it, organize them, then I right-click on the Sheet Set name and select Publish > Sheet Set Publish Options

In the dialogue box that opens I change four things:

1. Location: I point it to the network location where I want the DWFs stored.
2. File Format: change from DWFx to DWF (this is due to a limitation with our printing equipment)
3. Type: changed to Single-sheet file
4. Merge Control: changed to Lines Merge

It seems to maintain all of these setting until I close the sheet set out (change drawings, close C3D, etc.) Then when I reopen the Sheet Set later, it will revert the File Format back to DWFx and the Merge Control back to Lines Overwrite.

The reply given did not answer the issue but was mistaken for use with the plot dialogue box, which this is not about. The issue we are having is the sam as above with the "lines merge" ALWAYS reverts back to "lines overwrite"  after the sheet set is closed and re-opened. I have seen a thread suggesting that If the PC3 files are read only this may be the problem, but as a cad manager in even the smallest of firms, having the pc3 files read only is just about a must to keep from accidental changes from occuring. Is this the reason? I dont see what conection the pc3 files would have with the settings in the sheet set manager. (all of our pc3 plotter setting are set to "lines merge" in each of the printer settings as well) so, where and why it keeps reverting back to "lines overwrite".