Hi Rob ,

From your post i would guess that you have wound the cross slide in until the feed screw has disengaged from the feedscrew nut ?
Not knowing what machine you have makes things a little difficult as there are a few differing designs.
How far back in will it go ?
If you can wind say 5 or 6 turns before it locks it could be the gib strip being displaced .
What ever you do don't force it !
By the way welcome to the Forum and i'm sure there will be some one who either knows about or owns the same machine as you so help is not far away .

Ian

If you remove the top-slide you'll see a small gear wheel (if Super 7 with power cross feed). If so, whilst gently turning the cross-slide handle against the resistance, turn the gear with you finger until it engages with the keyway. When aligned the cross-slide will continue to move as it should.

If it's jamming remove the gib strip and make sure you can get it back in before you go for it more seriously

You may have to figure out a sneaky part of the refitting process first

Once you can do it without the gib strip, refit it and do the job properly