I recive that error in IE 8 (see the end for details).

Don't know if this applies, but Mr. Google returns this (seemingly relevant comment):

RE: IE explorer 'Expected hexadecimal digit' error
Ok, found it. It's a javascript variable referencing the Wordpress base path that contains back-slashes that are not escaped. This is effectively caused by the plugin. Will pick this up for fixing in a next release.

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; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MS-RTC LM 8; InfoPath.3)
Timestamp: Thu, 19 May 2011 16:58:55 UTC

Message: Expected hexadecimal digit
Line: 1
Char: 239
Code: 0
URI: https://Aserver/filesendr.nsf/sendFiles.xsp

Message: Expected hexadecimal digit
Line: 1
Char: 234
Code: 0
URI: https://Aserver/filesendr.nsf/sendFiles.xsp