Like many Google products, Google Calendar is still in Beta, and as such is not without its quirks and issues. It has been reported in several forums that importing calendars from Microsoft Outllok, while quite efficient and useful, can sometimes rsult in some corrupted events. While this isn’t a major issue–deleting the event corrects this–if you have hundreds or thousands of events, manging the problems can be quite a task. The problem is that if you really mess things up in yout main calendar, there is no way to "delete all" of the events short of deleting the calendar, which deletes your calendar account wiping out everyting. You can be very easily reinstate your account after deletion, but I have a suggestion that could make things easier….
Before you import anything, create a new personal calendar, and import any events into that calendar. Should your calendar somehow become corrupted, you can simply delete this secondary calendar without affecting your oher calendars or account.
Remember that Google Calendar manages multiple calendars simply and easily, so leveraging this to manage potentially corruptable calendars could save you huge headaches in the future, especially if you have taken the time to build and subscribe to multiple calendars.
Simply put, if you are going to try anything new or risky, use a secondary calendar instead of your primary one.
As always with any beta application, don’t commit your important information to it exclusively, or you may risk losing it. Google’s products have been, by and large, very stable, but it’s always better to err on the side of caution.