This is due to a security setting change within IE8 whereby the flash applet cannot control the behavior from the web browser. This seems to be occuring in Salesforce.com. However to overcome the issue you may do the following in the web browser to solve the problem.
a. Ensure that both the salesforce server (*.salesforce.com) and www.saleswebserver.net are in the same security zone (Internet , Trusted Sites etc.)
b. Within IE8 go to Tools / Internet Options / Tools / Security / (click on the zone) / Custom Level
c. Within the Miscellaneous section set ‘Navigate windows and frames across different domains’ to Enable
d. Restart IE8
Apparently this effect is by design within IE8 and cannot be overcome.