Upload problem: "'this.parentNode' is null or not an object"

Hi there,

When I try to upload files I get the following Webpage error details

"User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; FDM; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Timestamp: Wed, 7 Sep 2011 10:44:33 UTC

Message: 'this.parentNode' is null or not an object
Line: 5449
Char: 3
Code: 0
URI: http://mysite/files/js/js_c5de7da122c8ca0438287f0cd7edb562.js

Looking forward to suggestions.

Thanks,

JanPieter