will checkt out this evening , do I have to save the xml file from within wordpad as an xml ( changing extension ) ?
better take notepad, but save it before opening Renoise. If you do that while Renoise is open, it will overwrite your changes with the current session settings (which is the defaul value)
Would recommend using Notepad, sometimes Wordpad wants to put formatting and things in whereas Notepad will nearly always save clean (UTF-8?) as whatever extension you give it. Why I never edit html in Wordpad or Word.
Beaten by vV 
All right !!!
Setting the trecord buffer to zero , solves the problem .
I can now record a 512 line pattern without any lagging …great …
A small problem got introduced , when I select a whole track with the selection marker ( coloured overlay ) and then record some notes , I get lagging from the beginning , seems that that the selection marker puts a lot of strain on the cpu …strange …didnt happen in 2.6 .
Anyway I can live with this small problem , I just delete the whole pattern from the pattern matrix instead of using the selection marker .
Good job and thanks for adding the option to disable the recpord buffer .
Amazing develpoment team 
Shift F3 will do the same for the current selected track.
If you want to delete the whole track, selecting it with the mouse is more cumbersome anyway.
btw:Perhaps the more compatible Gfx updates in the GUI preferences has been accidentally toggled or might influence the erratic behavior?