Error 541 means "Invalid Attribute Value." Are you entering just the nameserver names? Any typos? Is that all that you're changing? Are the nameservers registered in the registry where you're trying to use them?
If you're properly spelling the names of nameservers registered in the registry for the domain you're trying to update, then it's likely a programming issue with your provider. Not knowing the domain or nameservers makes it tough to provide any more specific analysis. And, no, I'm not affiliated with eNom.