Sorry Fella,

I dont have an answer to your question as I cant just open Maya and try and tackle it, I create a poly I extrude- it works!

I figured you might have accidentally hit something while creating it -Locking translate in X or something I dont really know much about, but I'm a noob! KNOW many here can help if you're still suffering. Like me they probably assumed you got on with it somehow. Sorry again.

If it was me I would have just deleted that piece of geometry and tried again to get on with the Tute, as it doesn't really matter. Please don't get me wrong, I have a prob at the moment that doesnt 'really matter', but I'm still bombarding Miss_Nova with questions because knowing what to do when something isnt going right will help next time (and theres always a next time) Love to help you if I can, - Have you read my Signature? I'd learn something.

So some questions:-

Can you create a new poly cube in that scene and extrude a face in the X?

Is snap to grid on? If it is, sometimes it's awful hard to move a handle from certain angles.

Deleting that 6 sided Poly and creating a new one shouldn't take long. I know it doesnt help you know what went wrong, but will get you moving again - does it still not work?? If not then I'm even more intrigued - try resetting the tool (that tool doesn't really have many- but you never know)
Are you willing to post your file?

Send me a PM if no-one else who knows what they're doing jumps in with the answer and I'll bombard you with more questions Sadly I can't see an obvious solution which is why I didnt offer more help before.

IMO a new poly will work, and take 20 secs. The snap icons are at the top of your screen - They have little horseshoe magnets - they should not have squares around them.

If you select your poly and go to your Attribute editor, under 'Polysurface#' (# is a number) are any of your values greyed out? hit ctrl-a if you dont knowe where the Attribute editor is.

Umm yeah I'll shut up now...Hope something above works for you.