When you click on the help, the TRiLOGI program send the path of the browser and the location of the help file to Windows to request the browser to open the help file. So in case of IE, it is:
C:/Program Files/Internet Explorer/IEXPLORE.EXE C:\TRiLOGI\TL5\public\Help\content.htm
This works well with IE6 and I believe also with Netscape 7. However, the trouble seems to be that Firefox does not allow the local file path to be an argument. Instead it thinks that "c:" is meant to be a "protocol" (such as "http:" means hyperText transport protocol) and therefore it returns an error saying that "c is not a valid protocol" !!!
We are sending this problem report to development team and hopefully they will look into this in their next version release.
It is probably better for you to keep your IE browser even though you don't use it for day to day browsing. There are websites that don't work with Firefox so it may make sense to keep a copy of the IE6 on your disk and it will also work with the current TRiLOGI.