Dashboards slow on IE7, CPU spikes and lag when clicking on links

On a dashboard with a lot of content (Project portlets with 30 projects+, Activity streams), clicking on links have a 3~7 second delay with IE7. This doesn't affect IE8 or Firefox.

The delay appears to be on the client side, no request from the browser is sent until the delay completes. The CPU spikes during this wait. The problem appears contained to the dashboard only, clicking on links from the top nav bar does not have any delay.

This problem appears fixed in JIRA 4.1.