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the data you see on Hyperterminal? If so, well yes it could be all sort of thing, looks like a bad baudrate setting to me at first.

Did you tried a COM port sniffer to see how things are going between the PC application and the target board? A COM port sniffer also tell you the baudrate. I remember having few application which used weird baudrate and sometimes they changed from one baudrate to another baudrate value as well.

If you don't have access to any source code, that will be tough...