To reproduce the problem, process as follow :

• Download http://confluence.atlassian.com/display/JIRAEXT/Timesheet+report+and+portlet
• In IE8, add this legacy portlet in the DashBoard
• The portlet is shown with its Configuration mode
• Try to Save

The SaveConfiguration action is well called, but after the save, the Portlet is redirected again to the Configuration mode.
If you go to Developer Tools page (F12 or Menu Tools/Developer Tools) and access to the menu Cache/View Cookies Information, then the Save of the Portlet Configuration is available. The same side effect is you activate the Always Refresh From Server menu.

Other information, an error is reported by IE :
Message: Object doesn't support this property or method
Line: 9
Char: 1311
Code: 0
URI: http://localhost:8080/jira-4.0/s/466/1/1.0/_/download/batch/jira.webresources:jira-global/jira.webresources:jira-global.js

Any idea ?