The latest version of ChangeFSI is 1.15. If you are running the nested WIMP then it automatically assumes that you're running Risc OS 3.5 or later, which is not always the case. The code below allows ChangeFSI to work on all versions of Risc OS with or without the nested WIMP :
225SYS "XOS_SWINumberFromString",,"OS_Memory" TO ;f%
226IF f% AND 1=1 THEN version%=310
You should be able to insert these two line with any decent text editor. You may also want to keep a backup copy of the the 'ChangeFSI' file in case you make a mistake. If you do have trouble then email me (email@example.com) and I will send you the altered version.
Note : Due to various rules/regulations distributing the altered version of ChangeFSI over the web is frowned upon. However, considering what's happened at Acorn I doubt they care any more. If things go to plan (particuarly with RISC OS Ltd.) I will try to get this fix into the official version of ChangeFSI.