I still think it is the RSS feed, it seems to happen on the 3 every ten mins, for example 1543.
I have found the forum unusable recently. The most annoying part, if it kicks you out you lose where your were up to with unread posts. If I am catching up it prevents knowing where the new posts lie.
I am on 2Mb and the site is being hosted it seems through a 4800 baud modem.