Windows NT Server doesn't like file names that end in periods or spaces. When Mac users copy files ending in periods or spaces to an NT server, Windows clients connected to the server won't be able to access them. The same is true for file names that are the same as PC ports. These include:
com1 thru com9, lpt1 thru lpt9, con, nul, and prn
Most of the times in the past I had to rename these files, but that is almost impossible to do.
I have used this web site http://www.macwindows.com/index.html
Here is the software I use Mac Explorer:
http://peccatte.karefil.com/Software/MacExp/MacExpENG.htm
Take Care