[Users] typing x toggles ruler

[maxim]

Hi all

In Compose Message window, whenever i type a lower case x the ruler is
toggled, instead of x  being printed. Capital X is fine, but to get
lower case i have to press Meta-x. 

Obviously this is driving me crazy, and i can't find any setting to
turn it off. I have no idea what i did to switch this annoying
'feature' on - presumably i pressed a random selection of keys
simultaneously.

I've had a good google, but can find nothing on this, help appreciated!

thanks

max (aggh! can't even type my own name)