Buffering on streaming from Channel 4

Dell 2400 Dimension 2GB ram Ubuntu 12.04.

Internet avg speed download 2.9mbps.

I am having problems with 4od buffering on programs streamed from them. Generally this does not happen on itv.

e.g. If we start at 21:00 streaming say a 50 mins program it's ok for say 20 mins, them after that time buffering starts.

8 seconds of video and sound 2 seconds of buffering . very difficult to follow!

Note, there is NO buffering on any of the adverts even after it has started buffering on the main program.

Why is this?

We have notice that if we use pop out and close main browser, buffering is less likely.

I think that it is channel server....am I right?

Channel 4 say that they do not support LINUX. But they have said of late that they are working to resolve these problems ?

any help or advice would very helpful.

Thank you

Rich.b