parameter "i" in "mfg" is out of range

Hi the list, and merry christmas !

I am using some screen tool (screen, split.screen, close.screen) and at 
some point, I get an error :

parameter "i" in "mfg" is out of range

What does in mean ? How can I correct it ?

On the web, I find an old message from Giovanni that suggest to erase 
all the ".split" tool's, but I do not understand how this might works...

Thanks for your help
Christophe