David Morgenstern of ZDnet reported in his blog that file sharing problems with Lion/Lion Server and Windows clients is a known bug. We've had readers report similar problems, and another is below. Morgenstern quotes a report that pins the problem on files with extended attributes.

This rang a bell. In cross-platform file sharing with SMB extended attributes are usually mapped to NTSF streams. Which readers may remember, is something you can turn off in Lion and Snow Leopard get SMB file sharing working. We have a report on how do turn off streams with Lion here, and with Snow Leopard here. The result is the same for both: edit the /etc/nsmb.conf file (or create one) and add the line streams=no. Here a report about it for Lion, and one for Snow Leopard. (The later has more detail.)

So the question is, does this workaround have any affect on Lion Server when it comes to Windows clients? If you've tried this for Lion Server

Meanwhile, reader Chris Isaac describes the problem as he sees it:

I seem to have fallen into the role of looking after our 10 PCs and 6 Macs. I recently bought a Mac mini server, and decided to set it up just for file sharing and FTP, but with the intention of eventually taking advantage of some other Server services.

Under Snow Leopard, file sharing excellent with the Macs, and good with the PCs (all running XP Pro), then one of the PCs was replaced with a new one running Windows 7 - sharing from this was not so clever. Thus when I read that Lion server had a newer version of SMB that played better with Windows 7, I decided to upgrade. I set this going overnight, finished it off this morning, and now have complete chaos in the PC department!

None of the PC's can authenticate to the file shares, although I can connect from a mac using the same username and password that is being refused on the PCs.

If you've seen this issue .

For more on Lion Server, see Lion Server Tips and Reports