U use presta 1.7.4.2
Sometimes my control panel gets very slow, usually when i enter some other page, for example from order list to dashboard. Then, dashboard loads very slowly and when i try to open something else in new tab, it loads slowly as well. When page finally loads, spinning "loading" arrow in top left conrner keeps spinning. And after slowly-loading page finally loads, then when i open new control panel pages, everything loads fast as usual for some time.
I tried overwriting addonRequest function in Tools class but it didnt helped.