I did, a couple weeks ago. Market downloads wouldn't work on Wifi at my home, but it did on 3G and on Wifi at my work. After googling around and trying some suggestions, I ended up suspecting it could just be a problem with my home connection so I decided to just wait it out, and sure enough, last weekend it went back to normal.
Seems like internet links on Brazil, at least the ones based on embratel afaik (Virtua and the like, that I use at home and work) seems to be behaving very badly lately - while my home connection went back to normal last weekend, yesterday my work connection started acting up, though in other ways - connections to some sites in certain regions of the US was slow, while in others it was ok. Tracerouting made me suspicious of some kind of routing problem. So I did some trickery on my server's NIC that's connected to the ISP link to spoof a different MAC address for the NIC to force a new/different IP lease from the ISP, and that seemed to fix it, for now...
EDIT: I see you're from Campinas too - I live there, but work at São Paulo.