I found that pickpocketing only works once per NPC no matter your skill level; So if I pickpocket the Mayor e.g., steal his gold, and close down the loot window, then I am not allowed to try and pickpocket the other items again.
As some items are more difficult to pickpocket and thus greyed out depending on skill level (a good thing), this can actually break quests as I have discivered (the elf-orc feud quest line cannot be completed if you loose the argument to Victoria and pickpocket the elf for his gold and then have to wait for the second skill point to be skilled enough to steal the bloody amulet).
It should be possible to try and pickpocket an NPC as many times as one wants, maybe just add a higher chance of discovery the second time due to the NPC being aware he or she has lost something earlier.
Last edited by Gnoster; 04/05/14 05:40 AM.