Was the map built from scratch in GtkRadiant1.5 or has it been ported over from an older version or a different mapping program?
I had a similar problem when porting a map over from another game. What I had to do was go over it again applying the texture. I would recommend caulking everything then re-texturing the lot.
To make a jumppad you need a Trigger Push:
Key: target
Value: Jump1
Then a Target_Position to link too:
Key: targetname
Value1: jump1
That should resolve all your problems.