On Windows 7 Ultimate SP1, 64 bit (with Classic theme), and PasswordsSafe v3.29
Run Password Safe, enter passphrase to open database.
Switch to another window (often, but not always, by going to URL from PWSafe and auto-type logging in to web site)
Wait long enough for Password Safe to lock itself. (Possibly opening another window or two and switching between them, during this time.)
After PasswordSafe locks itself...
PasswordSafe appears in the task bar (configured as "combined when taskbar is full", if it matters), but when I click it the taskbar icon disappears (instead of activating PasswordSafe, to show the "enter passphrase to unlock" prompt) and I have to alt-tab or display the desk top to get to PasswordSafe.