I've had problems with Vista post SP1. Microsoft has special free support for Vista SP1.
To resolve a problem NOT related to SiDiary (I use 5 and PPC 5) MS Technical Support had me turn off UAC (User Account Control) -- but only because my locally installed firewall and anti-virus applications duplicated the protection of UAC.
FYI, I use ZoneAlarm Internet Security Suite 8 (with Anti-virus). Three or four apparently unrelated problems were resolved by turning off UAC.
It would be worthwhile to contact Microsoft Technical Support for Vista SP1 to get help with this problem.
Of course, YMMV!