lol. this was a pesky bug. heuristic wasn't working on one mssql test site and i couldn't find why. at end the problem was that when the HTTP code was raised (like 500) no parseResponse was called.

lib/controller/checks.py

@@ -444,7 +444,8 @@ def heuristicCheckSqlInjection(place, parameter, value):
 
     payload = "%s%s%s%s" % (value, prefix, randomStr(length=10, alphabet=['"', '\'', ')', '(']), suffix)
     payload = agent.payload(place, parameter, value, payload)
-    page, _ = Request.queryPage(payload, place, content=True, raise404=False)
+    Request.queryPage(payload, place, content=False, raise404=False)
+
     result = wasLastRequestDBMSError()
 
     infoMsg  = "heuristic test shows that %s " % place

lib/request/connect.py

@@ -266,6 +266,7 @@ class Connect:
             else:
                 debugMsg = "got HTTP error code: %d (%s)" % (code, status)
                 logger.debug(debugMsg)
+                parseResponse(page, responseHeaders)
                 return page, responseHeaders
 
         except (urllib2.URLError, socket.error, socket.timeout, httplib.BadStatusLine, httplib.IncompleteRead), e:

xml/errors.xml

@@ -23,6 +23,7 @@
         <error regexp="OLE DB.*SQL Server"/>
         <error regexp="SQL Server.*Driver"/>
         <error regexp="Warning.*mssql_.*"/>
+        <error regexp="SQL Server.*[0-9a-fA-F]{8}"/>
     </dbms>
 
     <!-- Microsoft Access -->