contaminated by dry hopping?

i've been brewing for several years but don't have too much experience with dry hopping.
i made my second batch of dogfish head 60 minute a few weeks ago (the first batch was outstanding!). almost 2 weeks ago (after 2 weeks in primary), i racked to secondary and dry hopped using a muslin bag, as i have done in the past. the hops were relatively fresh--i had ordered them for this batch a couple of weeks before brewing.
after a few days, the hop bag (i had weighted it with a large, sanitized stainless steel eye bolt as i had done before) floated to the top, and there was a shallow surface layer of foam. fermentation had restarted--about a bubble a minute--and almost 2 weeks later i'm still getting a bubble every couple of minutes.
obviously there were still some fermentables left after primary, and i have seen fermentation in secondary plenty of times, but never have seen it lasting almost two weeks with a scum on the top (looks more like scum than yeast foam).
any suggestions? i suppose i will keg it and see how it tastes.
TIA
ken

Did you sanitize the hop bag? I always boil mine first. I had an infection on a beer about a year ago and I kegged it and forgot about it for 6 months. When I finally got around to trying it and it was great. Some of my friends even asked me to make it again! (I couldn't even if I wanted to). Anyway, I would keg and try it. If you don't like it, try leaving it for a while and trying it again later. You might be surprised.

If you keg I'd suggest just using a stainless steel tea ball. Just clean, sanatize, fill with hops and drop it in the keg before or after you rack the beer. You can use two or three if you like and they work great. No muss, no fuss. They sink to the bottom and stay there until you kick the keg.

thanks for the suggestions. no, i didn't sanitize the hop bag. i will pick up a few of the stainless tea balls--a great idea!!

thanks

I started using women's knee high nylons (white) for dry hopping. The tea ball was always packed & I feared I was not getting the full benefit. I just soak the nylon in starsan before placing the hops in it. Cheap too. 33 cents a pair at wally world.