We have had this problem off and on, but I could not replicate the problem; however today I opened a PLC for a job that where I thought I had previously signed out. After clicking through the dialogue boxes I went on to Safari to check Architalk, and Entourage to check e-mail and then came back to Archicad. I didn't get any warning, so my draft must have still been current right? WRONG!! I continued to work for about 6 hours and after making all my changes, I went to send and receive changes only to be told that I am not currently signed in. It seems that by having Archicad in the background suppressed the warning dialogue box and I could not see it. There are other problems with Archicad's window management in OSX as well. If a dialogue box is up, when using Expose' you cannot see the box. Also, I am having problems that when other people are working on the file and I call up their section window, it appears (well it really doesn't) below my pallets on my second screen. There is no way to find this window without moving my pallets and relocating the window. It would be preferable if by using Expose' I could force that window to appear in front of the palettes.
Sorry, just needed to rant before I fixed my teamwork file.