Jay,  As Dan mentioned, this is a bug in Atmos.  We have plans to handle this better in the core platform, but don't have an immediate fix that will allow you to store an equal sign in a metadata key or value without encoding it before it's sent to Atmos.  You can indeed url encode (or quote) the data before it's sent and then decode it upon receiving it.  So in the case of an equals sign it will be replaced with %3D when it's stored.  Let me know if this is suitable a workaround.   Raj
I have some parameters in the form of an xml string that I want to use as a non-listable tag. I am ensuring that it's within the size limit for a tag (1k). Every time I try to create the new object in Atmos, I get the error "There was a mismatch between the signature in the request and the signature computed by the server."   I am wondering if there is some undocumented limitation in what can be sent as the value of a listable tag. The Programmer's Guide 1.2.7C says "use any characters from the iso-8859-1 character set", so why can't this work?
non-listable tag: value with xml gets a signature mismatch error