Hi Chris,
A bit tricky without more context. The only thing I could think of was it is an error from the XML parser we use for a lot of things, but that supports that charset. We do also use another XML parser for a few things but I'm not sure. Maybe check all the files the project is using to see if they're XML and see if they use that charset in the <xml> tag. If it's only happening on one machine and all machines are using the same files it seems unlikely to be that though, they'd all report the same error.
Regards,
Jo