un\locking does not set rw property on sln files

PushOk rwmon only restores readonly flag but never removes it, and it does
nothing when you use svn lock/unlock command outside of IDE. Readonly flag
restored when you externally commit file or pull its new version, this
actually means that files is not edited by you and therefore readonly flag
should be assigned to file for correct behavior of IDE.
When you use svn lock\unlock svn can modify readonly flag itself in case
svn attribute "svn::need_lock" exists for file. In your case probably all
files except .sln file has this attribute. If it is _really_ required you
can also add this attribute for .sln file. With this attribute source
control system will work in reserved checkout mode when only one user can
modify the file. This is reasonable only for binary files or for specific
files or IDE. Our plug-in, if configured in options, automatically add
"svn::need_lock" either for binary or all files depending on options
"Concurrent edit" options of plug-in configuration
(http://www.pushok.com/help/svnscc/index.php?redirect=ui_config1.htm).

Restoring the flag always happens if you change the file content.
In other cases, RW-Monitor can not determine that there was unlock.