I'm using 6.0.8_GA_2661 FOSS on Ubuntu 8 LTS.

When my clients are attempting to access a subfolder of a briefcase folder, they are hanging up their browsers. They see nothing until they move away from the page in question, then the error popup appears and the browser freezes (none of the buttons on the popup do anything). It's close-the-browser time.

Code:
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.3; .NET4.0C; .NET4.0E)
Timestamp: Tue, 26 Oct 2010 14:34:20 UTC

Message: 'this._selectedItems' is null or not an object
Line: 13000
Char: 1
Code: 0
URI: http://my.domain/zimbra/js/Startup1_1_all.js.zgz?v=100820045356

Message: 'this._selectedItems' is null or not an object
Line: 13000
Char: 1
Code: 0
URI: http://my.domain/zimbra/js/Startup1_1_all.js.zgz?v=100820045356
Yes, I know there is a "real fresh" bug for ZD with this same title; I'm not using ZD. And I (and my users) have this problem. Anybody else seen it? Got a suggestion?