I seem to be having the same issue again today. It occurred for a few days last week but seemed to resolve itself. Today however, whenever I login, I have to run xfwm4 in the terminal to get the min, max, and close buttons. Hopefully an update will be forthcoming that will resolve this.
Thanks a lot for your replies, I can confirm that your temporary "fix" works.
You might already know this, but I'd still like to suggest one thing that takes away the need for having to open the terminal and entering xfwm4 manually after every boot:
First of all - boot your computer, log in and apply the "fix". Close the terminal and open "Menu" - "Settings" - "Session and Startup". Click the 4th tab - Session - in the window that pops up. xfwm4 will be in the list as a part of the running session.
Noe just click "save session", close the window and you're done. Next time you log in you'll see that everything looks ok from the beginning.
Now we only have to keep an eye on the updates, and when something comes down I suppose all that is needed is to enter Session and Startup again and reset everything.