I used to have some problems with my g-keys. Turned out that it didn't type it fast nought. It used 0.1sec to do it and it messed stuff up. I could set it down to 0sec tho, but i have the Corsair software
What you have to do, to prevent it happening again is to go to LFS and write the text you want in there.. Then you go to the G-buttons in the logitech software and tell it to press that bind. (for example F2 for "Hello!").