PrintfText() is the central function to display text in the right side NFloattext object. Setting 
MUIA_NFloattext_Text requires the text pointer to remain valid after that call. But the typical 
calling sequence looks like this:

   allocate memory
   copy string to memory
   set(obj, MUIA_NFloattext_Text, pointer)
   free memory

And this is causing all the trouble (especially on AmigaOS4), because NList will be working on 
memory which is no longer allocated and hence crashes.

This fact is also stated in NFloattext's Autodocs:
         NFloattext don't copies the string into a private buffer
         as Floattext do it, so you need to keep your text in
         memory, but it uses less memory.

         If you want NFloattext to copy the text, just use
         MUIA_Floattext_Text which will do it for compatibility.


If keeping the pointer alive all the time is not possible without massive changes to the source then
a fix is still easily possible. NFloattext.mcc is meant to fully replace MUI's internal Floattext.mui
class and as such accepts attributes of Floattext.mui as well with the extent of some slightly different
behaviour in this case. Setting MUIA_Floattext_Text instead of MUIA_NFloattext_Text on NFloattext.mcc 
object will let NFloattext.mcc create a copy of the given text making it possible to free() the pointer
again after setting it. So just replace "MUIA_NFloattext_Text" by "MUIA_Floattext_Text" in define.h 
line 105 and the bugs should be fixed.