Gaius Maro never actually enters cities....

[Zephorah]

...is this a resolvable bug?

The assassin quest says to kill the man in a city for a bonus. The quest also offers up the ability to track Maro via a stolen itinerary. I can follow him a few paces behind, in which he simply walks past the cities. Or, I can wait inside the city at the appropriate location he'll be on a given day/time...then use "M" to watch his map marker slide past the city and never actually enter...

Is it possible to kill Gaius Maro inside a city or is this bug such that I should just give up and kill him on the road?

[Shelt]

I killed him in Whiterun in the tavern I think. He actually does enter cities. Try waiting in one of the cities and advance time by an hour or so until he shows up.

[Zephorah]

I waited half a day in windhelm, then fast travelled to riften...he just passed both by...

[Trigger]

try, Verify Integrity of Game Cache-if only one file fails to validate your game is okay, more then one file failed-means your game was missing game info and will be replace automaticly....Right click on Skyrim in your list of Games, Left click on PROPERTIES, Left click on LOCAL FILES, Left click on VERIFY INTEGRITY OF GAME CACHE= will take afew moment to do it's thing, then close, then press play, the game will detect your graphic's card and set it's recommend setting for you.

[Vita, Mortis, Careo]

I kill him at the Bannered Mare every time. Knowing that the quest is wonky, I will enter, use the wait function until the early evening and then voila, there he is.