Looks like you're exporting out a HDV sequence. HDV has a different PAR (pixel aspect ratio) then 1920x1080 HD and different from 720x576 PAL. That's probably why your stuff is looking stretched. The PAR is wrong, given that you setup your timeline as a HDV sequence.
I would recommend transcoding your footage to one common format. Either 1080HD or DVPAL depending on your output and needs.
— Change your timeline settings to a standard 1920x1080, square pixel aspect. This will require you to readjust the HDV and PAL clips on your timeline (possibly scale them to fit).
— Change your export settings to do the conversion to 1080HD