While Oracle does recommend that you upgrade the clients, you can use the older version, however, you may not be able to take advantage of newer features on the client.
Be aware that there can be undocumented side effects of a DB upgrade on your clients. I recently had to tweak all ODBC driver settings going from 8.1.6 to 8.1.7.3 on NT (disable query timeout and bump up the fetch array size).
http://metalink.oracle.com/metalink/...d= 213135.999