Hi mate', Im in double glazing for a living. Sounds like your door has dropped which is a common fault and happens to most doors. To rectify this you need to take the beading out that holds your glass or panel in, and packer the corners with plastic glass packers to 'Toe & Heel' the door sash, which is the part you open.
If the door is under guarantee get the Company back out to sort this as it is more of a specialist job to get your door set up right and lining up the locks and taking the beads out without damaging them etc.
Hope this helps.
David, May 2009
