Didn't even notice that when I bought mine over a month ago! haha. I've been on 25mg of zoloft for about 4 months now, and actually started weening myself off when my Npro arrived in the mail (just a coincidence) and have been on the medication for atleast 2 weeks while
vaping the hell out of my Npro. I have had no problems at all.
Prior to e-cigs, I've been chewing Nicorette for months while being on Zoloft, and had no issues as well.
IMHO, I think that warning is just a pre-cautionary statement, and granted, I don't know how nicotine reacts with Anti-D's, but I know alcohol can be fatal if you drink too much while on them. So who knows!
Everyone is different though, so if you are interested in e-smoking, I would recommend you
vaping w/ low nicotine content and take it from there.
Hope that helps.