Make sure that:
1. You send a session id to HSBC. "Force Cookie Use" should be turned off if you use HSBC.
2. When tesing make sure that the total purchase price, including postage, is less than 50 pence.
3. If your site uses a template it's likely that the session id may get lost before checkout_confirmation, so do a "View Source" to make sure the session id is present
4. If your server is based outside of the UK then the server time zone will be wrong, and the code need to be adjusted for it. One hour, plus or minus GMT is all that HSBC will accept.
Vger