This has been fixed and is available in the SVN. The fix will be available in the next release.

Basically the 'unescapeFilePostParams' function doesn't check to see if the 'file' argument is not undefined before trying to work on it. Here is the corrected version:

SWFUpload.prototype.unescapeFilePostParams = function (file) {
var reg = /[$]([0-9a-f]{4})/i;
var unescapedPost = {};
var uk;

if (file != undefined) {
for (var k in file.post) {
if (file.post.hasOwnProperty(k)) {
uk = k;
var match;
while ((match = reg.exec(uk)) !== null) {
uk = uk.replace(match[0], String.fromCharCode(parseInt("0x"+match[1], 16)));
}
unescapedPost[uk] = file.post[k];
}
}

file.post = unescapedPost;
}

return file;
};