I have done 2 "special jobs for him" the White Run job to get arin released by changing the book and removing the letter from the Jarl's quarters

The windhelm job by killing off the rival thief's guild (silverbloods I think) BUT evertime I go back to Delvin he still says thanks for both of these jobs. Can any one tell me why? I still have the skeleton key I have not finished that quest it that the reason? (thiefs guild quest) to return it to the http://elderscrolls.wikia.com/wiki/Twilight_Sepulcher. I intend to keep it till I get the unbreakable lockpick skill perk.

thanks

Not sure why. All the special jobs I've done keep showing up in my dialogue with him, and he keeps paying me for them.

Patch 1.6 broke the functionality of the "say once" flag on dialogue. If you save and reload the topics will be gone. There's no problem with clicking them again, you'll just keep getting more gold each time you do.