Problem:
wasp ERROR "org.xml.sax.SAXParseException: Character reference  is an invalid XML character"
Cause:
Special characters in target field can cause wasp errors
Resolution:
You can find these special characters (such as CTRL-Y which turns out to be the  in HTML) but running a query like this:
SELECT target, probe FROM S_QOS_DATA WHERE target LIKE '%' + CHAR(31) + '%' and created >= '12/16/2010' GROUP BY target, probe
This will provide the offending target, from there, you can find the probe source in Infrastructure Manager, then you will need to not only delete (or fix) the bad configured resource, but then also delete the QoS from the SLM, and reset the group_server tables.
By the way, you can use special editors (example, hex editor) to see the special characters in the config files. A specific example would be XVI32 which can be found here:
http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm