I'm trying to sync my library (which has recently been sync'd) after the addition of only three references, but I keep getting an error message as follows:

[JavaScript Error: "The service is not available. Please try again later." {file: "chrome://zotero/content/xpcom/sync.js" line: 2112}]

[JavaScript Error: "[Exception... "'Invalid response from server' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001e (NS_ERROR_XPC_JS_THREW_STRING)" location: "<unknown>" data: no]"]

I'm using Firefox 3.6 on a Windows XP SP3 system, with the Zotero 2.0 add-on.