ODBC - Invalid protocol character

When using the odbc driver from Access in Win9x we sometimes receive the
error message "An invalid protocol character was received from the
backend".  While this could mean that someone passed gas, I don't think
so.  Anyone see this before?  The one particular query that gave this
error is:

SELECT Description AS "Item", SuitabilityName AS "Suitability",
AgeGroupName AS "Age Group", SizeName AS "Size", Qty AS "Quantity",
tblStResTree_cache.SurID
FROM tblListRequestItems, tblIdSuitability, tblIdAgeGroup, tblIdSize,
tblStResTree_cache
WHERE tblListRequestItems.SuitabilityID = tblIdSuitability.SuitabilityID
AND tblListRequestItems.AgeGroupID = tblIdAgeGroup.AgeGroupID
AND tblListRequestItems.SizeID = tblIdSize.SizeID
AND tblListRequestItems.TreeID = tblStResTree_cache.TreeID
AND RequestItemID=3;

It really doesn't look strange at all, so I'm not sure what's wrong.  
This happened a while ago and things have changed since then so I'm not
sure if I can reproduce the error or not.  If needed I can dig through my
archive in a little and try to give a stable test case for this problem.

-Cedar