Communication error with Vaadin 6.8.8

We are experiencing a communication error in this red box in the browser when a % character is inputted into a textfield

Communication problem

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(SyntaxError): missing ) in parenthetical stack: HV@ UV@ tm@ Tm@ d.onreadystatechange<@ Rb@ Ub@ @ fileName: lineNumber: 1806 columnNumber: 0 - Original JSON-text: html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “”>

I have not been able to find a solution so far and migrating to Vaadin 7 is something we would like to avoid at this point. Appears to be a problem with Vaadin’s JS. Any hints?

Any help is greatly appreciated!