Hi Andrew,
First make sure that you have full supervisor rights to both the SRASP directory and the data directory. The fact that you have the option to convert one of the data sets and not the other suggests things installed OK.
Then rename/remove the saasp directory. Sales Analysis 6.5 has a prefix of SR, and installs to a different program directory than 6.1B (thus the reason why both appear in the list of installed versions).
Remove the references to your Sales Analysis data from the WSM start list where the program is SA. This is no longer valid. If you use this start list, because you still had the old Sales Analysis present, the program will still be happy in loading the data in the old version. Make sure you only have 1 start list entry for each of your data sets, and the program is SR for Sales Analysis 6.5A for each.