A B757 flight crew failed to cross an intersection at the prescribed altitude when flying a charted RNAV Visual approach to a foriegn airport. Fatigue and inexperience in type were cited as contributing factors.

Narrative

First Officer was flying. I was pilot not flying. We were on our second leg of a back side of the clock launch. We were arriving into the airport. Previous clearance was to proceed to the NDB; descend to 4;000. ATC asked if we had airport in sight. I responded; negative we are looking directly into the sun. ATC said no problem. First Officer set 4;000 in ALT window and I confirmed 4;000. We were cleared via the RNAV 26 charted visual approach and to cross the next intersection at 4;000. Approaching the intersection we were able to see airport and the First Officer was slowing to begin configuring for approach and landing. At the intersection I noticed that we were at 3;600 FT descending. I immediately said to 'climb back to 4;000'. The First Officer aggressively climbed back to 4;000. ATC came up and said to climb. We quickly leveled at 4;000 and reported level 4;000 to ATC. ATC said thank you and did not seem to have a problem with it. We landed uneventfully. We were both tired. I was a bit distracted looking directly into a bright rising sun and trying to locate the airport and runway visually. The cockpit glare was intense.Both the Captain and First Officer are new on the airplane and had less than 100 hours. The company has a waiver for us to fly together with less than 75 hours in type. In the highly demanding Europe environment; I do not think this is a good idea.