Running a late 09 MacBook - 4 GB RAM -- PD 6 (latest update) Windows XP. I don't think this problem is directly connected with the 10.7.3 update to Lion -- but I've noticed it since then. PD 6 is just randomly starting and launching Windows. Note in my Parallels Configure prefs for XP I don't have XP launching automatically if I were just to start PD from the Dock or Applications. So -- some Windows process must be triggering a full launch of XP. I've noticed it when I just open one of my browsers or at other random times. It's so annoying. And I should say usually when it happens PD 6 and XP open "Hidden" I don't even see it - but I know it because I here the Windows XP login music. Finally, if I were to go to applications folder and double click on Parallels desktop -- then it would become visible because it was already open.
In Parallels, select Virtual Machine -> Configure, then select Applications -- what is your setting for Share Windows applications with Mac? I had that enabled for a while and just kept getting annoyed, as some file types were set to open in the Windows app and that would launch Parallels. I wonder if something similar is happening on your end? I only ever use Windows apps in the full-blown Windows window, and pretty much never want to use Windows apps side-by-side with Mac apps, so I disabled this setting. Hope this helps,
Thanks for that advice. Had done a complete wipe and reinstall of Lion in the past week and this problem with Parallels had not come back since. I will consider turning off sharing next time if the problem reoccurs.