When AjaxFileUpload post back it takes your page URL and appends onto the end of it it's own query strings (contextkey and guid). This works fine if your page URL doesn't already contain any query strings but if it does then you end up with a URL that contains two question marks which then corrupts your own final query string value and this in turn stops the upload from working.
Comments: instead of just replcing the lines i did a validation to cover both posibilities Line 176 if (this._postBackUrl.indexOf('?') == -1) this._webRequest.set_url(this._postBackUrl + '?contextkey=' + this._contextKey + '&guid=' + this._guid); else this._webRequest.set_url(this._postBackUrl + '&contextkey=' + this._contextKey + '&guid=' + this._guid); Line 375 if (uploader._postBackUrl.indexOf('?') == -1) uploader._vForm.action = uploader._postBackUrl + '?contextkey=' + this._contextKey + '&guid=' + this._guid; else uploader._vForm.action = uploader._postBackUrl + '&contextkey=' + this._contextKey + '&guid=' + this._guid;
Comments: instead of just replcing the lines i did a validation to cover both posibilities Line 176 if (this._postBackUrl.indexOf('?') == -1) this._webRequest.set_url(this._postBackUrl + '?contextkey=' + this._contextKey + '&guid=' + this._guid); else this._webRequest.set_url(this._postBackUrl + '&contextkey=' + this._contextKey + '&guid=' + this._guid); Line 375 if (uploader._postBackUrl.indexOf('?') == -1) uploader._vForm.action = uploader._postBackUrl + '?contextkey=' + this._contextKey + '&guid=' + this._guid; else uploader._vForm.action = uploader._postBackUrl + '&contextkey=' + this._contextKey + '&guid=' + this._guid;