As happened with the two sites I mentioned above talkimg may have problems because it cannot upload images, while Imgpeek runs normally. As simple as that, it's an alternative.
FYI, this error you are showing of Talkimg, isn't really a problem at all. In fact this particular error been discussed many times in Talkimg's thread. It only happens when you keep the tab opened for very long time. Just give the site a quick refresh, and you won't see that "access denied" error anymore. Reason behind this is expired credential connection, said joker_josue. Apart from this I rarely saw any issues.
But I do belive two is better than one. It doesn't really hurt keeping alternative as reserve.
For security reasons, sometimes, when the page is open for a long time without activity, the server turns off the credentials connection (let's call it that). Even when browsing the site, the upload system may not work correctly. If this is the case, try closing the tab and reopening it or force refreshing the page so that it loads new credentials.
