when using IE7 or IE8 to open some e-mail messages (ajax webmail), it's very slow.
It takes from 20 to 30 seconds to open some messages. Apparently the affected messages has nothing special (no attachments).

The ZCS version is 6.0.10_GA_2692.UBUNTU10_64 UBUNTU10_64 FOSS.

I suppose the problem is on the javascript engine, since the html version of webmail works fine on IE. No problems opening the same messages with firefox.

Is it a known problem, or can it be solved with some settings?
Thank you in advance for any hints.
Best regards