XFCE reverted to default desktop without my having changed it...
 

slack64 -current, this odd behaviour occurred this am on first boot...anyone had this happen to them before?

The system default can be set via xwmconfig (you can see what the default is by which symlink exists in /etc/X11/xinit), which will be used if no local Xsession files are found (~/.xinitrc). If you say you didn't change it yourself, perhaps you deleted ~/.xinitrc and thus reverted to the system default.

no, I didn't delete anything...puzzling, I've go not title bars on apps that I open and drop-down menus aren't working either...hmmm...must check logs...

Did you enable compiz? What your describing sounds like it.

as I understand it, compiz is a desktop effects thing for KDE...I don't use KDE and if compiz is enabled by default, then it has always been "enabled" on this laptop since I installed Slack. To restate, I made absolutely no changes to anything on this machine yesterday when I used it, and when it booted this am, XFCE reverted to a default desktop and the problems with title bars, drop-down menus and now I notice that I can't resize windows either...very puzzling...

Oh, I thought you meant that your DE changed from something else to XFCE.

If you really made *no changes* (install any packages? touch anything in ~/.config?), try using KDE and see if compositing, resizing etc. works.

further reading leads me to suspect corrupted cache/session files on logout/shutdown, so doing
rm ~/.cache/sessions/xf*
appears to have cleared out the cruft and all is as it should be
props to member Ilgar from Istanbul

Compiz is not part of KDE, it is a component of X11 and is not enabled by default. I have seen many users in the past describing the similar issues as you and it was due to compiz being enabled and not configured properly.

Glad you got it sorted.