Good afternoon.

I have a recurrent problem consisting in the following:
- I connect and begin playing without lag.
- At a certain moment (not related to any certain period of time, or action, or at least not apparently) I experience what looks like a huuuuuuuuuuuuuge lag: I can move, but I cannot cast any spell or interact with NPCs/players/artifacts, every other player character gets frozen, my messages do not appear in the screen, etc.
- BUT, when I reconnect my messages have been sent and my PJ appears in the same exact spot where I left it after wandering during the "laggish" experience. Even more, the items that I have tried to move within my inventory are moved and I have picked up items from corpses/containers...

I have not found any possible source that this problem might steam from yet.

Help, please!!!

Additional Data:
I play on WOTLK 3.3.5a Lordaeron Server.
I have not updated the game to the WOD character version.
I have noticed that the latency does not go up when I experience this problem. My latency is always below 100ms.