Did you had weapons in ANY of your slots?
Only first slot matters.
When you went to Junktown, did you have your weapon on and get past the first gates without holstering your weapon? My guess is that is was either just lag or maybe those NPCs don't do the 15 second wait, just the ~5 second wait like pre-wipe?
It if it the 15 second wait thing, then you could have probably ran to the store within 15 seconds of entering the gate, so they just started shooting you as soon as you entered by coincedence.
On a side note, this topic is like warning everyone not to carry a gun in Junktown, even though they should know not to if they bothered talking to the guy at the gate.
