Inspiron 6400 wont work properly after waking from sleep, since I resintalled Vista

Sleep / wake always used to work on my Inspiron 6400 purchased in Jan 2007 with Vista Home Premium.  However I reinstalled Vista (from a Vista disk, not the recovery partition), downloaded  all the MS updates and now when I wake it from sleep or hibernation it as often as not doesn't work properly (e.g. some applications like Outlook, Explorer wont open). When I try to restart it it justs sits there saying Logging Off for hours until I reset.

I also tried downloading the drivers from Dells website, but this didn't seem to help.

Any ideas anyone?