Yellow triangles.

Recently while playing ET I have started getting yellow triangles in the lagometer every few seconds.



When they occur I lag out for a split second, so it's pretty annoying to play with. Is anyone else having/has had a similar issue and if so how did you fix it? Otherwise does anybody have any idea what may be causing this or how I can fix it?

Thanks :o)

Edit:
I'm on ADSL2+, no wireless.