Due to the way the SI5.5 file manager works, it is important that SI5.5 server and desktop applications are time-synchronized to ensure no loss of data. This posting provides some instructions on effective ways to do that, as suggested by Microsoft.
When checking out a project, the desktop application receives a timestamp from the server. Let's say that's 2:00 pm server time. When the desktop user, whose clock is at 1:30 pm, decides to check in the project, the server thinks it has a newer version of the file and overwrites the changes that the desktop user made.
Short-term – synchronize the clocks on the server and all desktops.
This is the default behavior in a Windows domain environment. Click here to read a Microsoft article on this subject.
In a workgroup, you can synchronize to an internet source by following the instructions here.
For Vista, there are no Microsoft articles but this blog entry has some useful tips.