I recently updated my website with the dll patch telerik provided for the cryptographic weakness: http://www.telerik.com/support/kb/aspnet-ajax/details/cryptographic-weakness?utm_medium=email After the update I found that the pages which were using the RadEditor control and several other controls was not loading and throwing this error: Parser Error Message: Decryption key specified has invalid hex characters. Several other controls are throwing this error but I cannot delete controls one by one and check which ones are having this problem. But I checked for the RadEditor and it was throwing this error. Nothing else is there on the page while testing other than this control. This does not happen on a plain new website and is happening when we have the sql mermbership and machine key configured. We are using passwordFormat as encrypted in sql membership config and cannot remove machine key. If you got to test it, then test it on some already configured machine key and sql membership website. I have attached screenshots for this error and telerik dll patch in use currently. We are on a production server and we need a solution for this issue ASAP.