Thieves Guild Special Job Bug

I completed enough thieves guild radiant quests to get a "special" job from Delvin. I talked to Delvin to get the special job, and there was nothing added to my quest log. Now every time I get near him he tells me my work has been noticed and that we got a special job, but I can't get a dialog to appear with him.

When I talk to Vex, she says I have to complete Delvin's special job before I can get anymore work.

Knowns.

1. Quest is not in my log.
2. Reloading a previous save game is not an option.
3. I left Riften and did another series of quests and was gone for about a week of game time.
4. The main quest line is complete.
5. The thieves guild (nightingale) quest line is complete, though I may not have the thieves guild armor anymore as I preferred the dark brotherhood gear.
6. It is on the XBOX 360, so the console is not available.

Any suggestions?

You could try going to the people in the major cities who are the starting point of the quests, outlined by this guide:

http://elderscrolls.wikia.com/wiki/Thieves_Guild_(Skyrim)#Special_Jobs

NOTE: There are spoilers and walk throughs on this site.