I'm trying to use the Edit in Photoshop function in LR2.3 (using PS CS3). The creation of the -Edit copy and export is fine and PS opens the .psd fine.
However, when I go to save the file in PS, PS tells me that the file cannot be saved because the file is already in use or was left open.

so all I can do is do a Save As which really doesn't help.

Has anyone seen this behavior before? The only thing I can think of is that the files are all on network attached storage (ethernet external drive).

This appears to be a network storage issue. It happens on afp or smb mounts but not local disks. bug has been filed w/ Adobe under LR.

fantastic