We're encountering fairly frequent issues of Microsoft Project files
stored in MOSS 2007 team sites as being checked out when a user
attempts to Edit in Microsoft Project when there is no indication in
the portal that the file is actually checked out. Has anyone else
encountered this? Is this a known issue? Workaround suggestions? User
error?

I hate to republish the file with a new name and split the versioning
stack, but that's what we've been doing.