I recently got a replacement Treo and somehow ended up with all my past Calendar events duplicated. My Contacts were not duplicated.
I applied "Find Duplicates..." (Edit menu) in NUTD and used Automatic Merge. The merged removed all duplicates as desired, but changed all upper case letters to lower case.
I created a backup luckily and tried again, this time using "Keep New" which eliminated all the duplicates too, but again made everything lower case.
I used Title as the criteria. Then I tried Body, First Date, Last Date and unchecked Title. Now the title remained upper/lower case, but all the body text was changed to lower case. Ugh.