A bug has been reported in version 3.5 that will cause the program to terminate if you use the Move up or down functions in the Transaction History from Customer Details. This does not affect moving transactions through Reservation Details (where it's most likely to be needed) -- only from Customer Details.
In case you're not familiar with this feature, this was a new feature in version 3.5. It's primarily used to change the order that payments and charges are listed in a customer's Transactions (usually only necessary to correct "Uncategorized" entries on the Receipts by Category report).