There should be a whitespace before tag. It can be not obvious in JSP code, but the exception tells, that probably a new line char has been already sent to HTTP stream (JSP container implicitly opens HTTP stream for that). tries to open the stream again, and causes the exception.

As I wrote, for different JSP containers the situation has a different severity. On Win it is just a warning, on Linux it could be fatal.

Could you please just copy paste a top part of your JSP and publish here?