sharing folders

Do both parties have to be set to Online to get share to work? I think not
but want to confirm.

Are there limits to file size to be shared?

Had it working fine with a contact but now it doesn't seem to ever finish
sync with a couple video files.
At times it reports 0% at the other end. At this end it reports file name 0%
done.
We had about twenty pictures which shared right off when first setting up
share a week or two back. It's not our connections speed because they send
quickly in chat window. Couple of small txt files went through fine in the
sharing folder.

Really getting frustrating since I was able to share an hour video tape to a
third party with no difficulty. That suggests this end is fine but neither
of us made any recent changes since first setting up. Other party removed
out of date Norton and installed AVG two nights ago. That didn't help
either.
(The txt files shared since AVG changes).

This morning it's reporting Synchronizing for more than 3 hours. Should have
been done long ago.

TIA