Org Mode iCalendar export non-unique UID generation

I am using Emacs 23.2 and I am using org-mode to keep track of my tasks. I have quite a list of tasks that I have made up as events by mentioning the time period and adding the SCHEDULED tag for the tasks.

When I export the task to the iCalendar file, using the C-c C-e i command, I get the .ics file but many of the tasks have the s开发者_JS百科ame UID even though the date and the time stamp mentioned are different. Why is this so? Is there a way I can generate unique UIDs in org-mode?

I tried customizing the UID format variable to %s%temacs and some other list of format specifiers in the customization but it does not seem to work.

Has anyone faced this kind of a problem?

Thanks Shyam