Windows XP/Vista/7 Laggs and ping issues

Dear Legends Staff and members,

It has been a while now that I sometimes encounter serious laggs (call it ping if you like) which is described like this: every 1-2 seconds of game running smoothly are followed by 10-15 seconds of a complete freeze and it goes like this for hours.
I have checked my connection, router, and even opened youtube video to check my Internet connection - and its fine, which means it is only in Legends. everything else works fine.

I did noticed that right after a Server check (and the following 5 hours or so), I don't have that problem at all and the game runs smoothly.

What could be the cause?
And how do I fix this?

Please help because I cannot play this way it is a torture and frustrating.

Appreciate your help,
Spyro.