Keyboard autocomplete - v6 errors

I’m in the process of moving over to R6 from R5 and I’m having a problem with entering commands via the keyboard. On V5 the autocomplete function works very well.
On V6 it doesn’t seem to be working. I’ve tried setting and unsetting the tick boxes under options - appearance - keyboard autocomplete, but as i type a command in, the list jumps from letter to letter, so typing MOVE will offer me the commands from M, then the ones from O, then V etc.
With both autocomplete options unticked, I can’t enter any commands in to the command line - the first letter entered disappears and hitting enter starts the last command used.
Any suggestions for correcting this would be great, as I’m a bit stuck in my ways using the keyboard as it is the fastest mode for me to get my modelling done.