SELECT INTO TEMPORARY problem

I have a servlet which gets its data through a DataSource (Tomcat 5.5)
and starts each request as a new SQL transaction and either commits
the transaction or rolls it back at the end of each request.

In one of the requests I do a SELECT ... INTO TEMPORARY t1 ..., which
works just fine when I first use it, but from then on it objects saying
that t1 already exists. When I read the documentation (8.1 as that is
what I am using) I thought I understood that the table would disappear
at the end of the transaction. Other than deleting it, is there something
else I need to do or have I missunderstood that into temporary does?

David