Notes/Domino 4 and 5 Forum

I am using a class in a script library which has worked properly for years. I am now editing the class and it will apparrently save ok and compile ok and run ok but when I open it again there is text missing at the bottom of the class and I have to fix it before I can carry on or close without editing.
I have copied the complete contents of the class into a text file and tried to paste it back in. only a type that I declared before the class will paste in and the class will not. If I only paste in the class then the full class will paste in but I still get the missing text problem.
I have tried creating the type as class in its own right in another script and just getting to it as an include but I still have the problem of the text not appearing properly when I open the class in designer again.
the compiled code is still ok but I won't be able to edit it or any other code safely on the live system until I get to the bottom of this strange occurrence