Calendar form not visible

When I create or open a calendar event, I cannot see the event form. The
form is opened, but not visible. I can see that the form is open by looking
at the Taskbar or by ALT-TAB to the window. I cannot select that open
window, however.

I can edit my calendar events when I open Outlook in Safe Mode, and also
when I open Outlook normally when I boot into Windows Safe Mode.

I have deleted all my plugins. I cannot clear the custom forms cache. I
get an error that says "Unable to open dialog box. No pages in the property
sheet due to low memory. Close some windows or programs." I have deleted
all copies of FRMCACHE.DAT. Still no change. I have made no hardware
changes. My hardware tests good.

I have uninstalled and reinstalled Outlook. No change. I backed up and
deleted my PST file, and tried to create a calendar event in a new PST. No
change.

The problem manifested itself after I imported a flight itinerary from Delta
Airlines ad a calendar event. I have since been running Outlook in Safe Mode
for three weeks.

I am not sure where to go from here. Help?

Thanks