Formatted dates have swapped values
Inserting a formatted date may result in entries where the month and the day are in the opposite positions. The symptom usually appears with Regional Settings using a non-US format.
I've had reports that resetting the values to default fixes the problem. On Vista/Win7 the Reset button is located under Control Panel>Region and Language>Additional settings.
RM_TEMPNAME
If the program crashes unexpectedly in the middle of a renaming operation, you'll see a list of files with the extension RM_TEMPNAME. To remove this temporary extension with Rename Master, set the filter to *.RM_TEMPNAME and Replace the entire extension with nothing. This will restore the original file extension.