Impact Suit and all the individual modules store preferences on the local hard drive.
These preference files are stored in the folder START->MY DOCUMENTS.
ISSUE:
Preference file has gone bad, the preference file is corrupted or my preferences are not set correctly.
SOLUTION:
You can reset your preferences back to the 'factory defaults' by following these steps:
Close ACT!
Go to START-> MY DOCUMENTS
Rename the folder 'Durkin Impact v5" to 'Durkin Impact v5 OLD'
Restart ACT
Sometime you can be more surgical by only resetting preferences for an individual module. TO do this open the folder 'Durkin Impact v5' and rename the module preferences such as: Renaming 'Durkin.Views.Calendar' to 'Durkin.Views.Calendar OLD ' for Calendar View Plus