It is definitely a problem.
In my case a Win XP system.
Lion -> Win XP no problem
Win Xp -> Lion mount Read/Only
Boot Lion machine with 10.6.8 - no Problem mounts R/W.
Some have reportedproblems involving home directories, but in this case it a separate volume not the Lion or 10.6.8 volume.
I have reported it to Apple.
I am experiencing somewhat of the same issue.
When I try to open an excel document located on my lion server from a windows machine I get an error saying "File cannot be accessed. The file may be read-only, or you may ben trying to access a read-only location". I can however create folders and copy over documents no problem. This makes absolutely no sense to me.
You described my situation as well.
I have a Windows XP computer -> Lion SMB share that mounts correctly but has "challenges"
- Files and folders can be created but error messages are displayed on the Windows side. Refresh the window and they are there.
- Files and folders can't be renamed or deleted
A Snow Leopard Mac on the same network -> Lion SMB share works great
Prior to upgrading to Lion the same shares on Snow Leopard worked flawlessly.