Doors and Windows - restore casing window

i am repainting the house and have a vertical hinged casement window. the window is bowed slightly such that the lock near the bottom works however the lock near the top because of the bowing will not work because the window will not close squarely to the frame. any ideas or suggestions to remedy this problem?

Thanks

hmmm...i am wondering if its possible to remove window...sand frame....apply some magical solution to the wood and let cure/dry with extreme weight on the frame on a flat surface?

It's hard to say what the problem is w/o seeing it. If the side of the window that latches is really "bowed" as you say, and you've checked it with a straightedge to varify this, then what has likely happened is that the wood frame has separated from the glass. With most casement sashes, the glass and glazing are what hold the rest of the sash square. If the glazing has let go or slipped, then the wood could bow away from the glass. If there is a removable wooden stop on one side of the glass or the other, you might be able to remove it, clamp the window back into shape (bar clamps) seal the perimeter of the glass with 100% silicone and then reinstall the stops. You could also force the window shut and then pry it over, keeping it pressed over with some shims inserted between the sash and the frame. Leave them there for a few days until the silicone has set.

Something else that can happen is that if the window has a metal or vinyl "fin" weatherstrip, it can become malformed and cause problems with the window shutting all the way.

If the window is out of square and is dragging on the bottom or hitting the frame on the top of the latch side, then the solution may be similar to what was discussed in paragraph 1. The edges of the glass may have slipped down around the glass due to poor shimming around the perimeter of the glass.