Paypal Payments Standard

I am trying to complete setup of a new shop and have enabled the Paypal Payments Standard gateway in Open Cart (version1.5.6.4).
I have set the email address to the relevant one in Paypal that the payments need to go to and transaction method to sale. ( Not on sandbox mode).
At the last stage of checkout the customer presses "Confirm order" and should, presumably, be taken to a PayPal log-in so that they can pay.
Instead of the Paypal log-in a message appears with the Paypal logo and "Things don't appear to be working at the moment. Please try again later".
Have I got a setting wrong somewhere or does this particular method no longer work with Paypal?
Thanks, John

If its any help, this is the url of the Paypal page:
https://www.paypal.com/webapps/shopping ... NPUT_ERROR

Re-enter you details again and check you have not invalid characters or spaces.

I hadn't thought of looking for extra spaces, but with your advice I checked. There was a 'rogue' space at the very end of the email address after the 'uk'.
Removed it and 'hey presto' we're in business.
Thank you indeed for the assistance.
John

I have the same problem, I double check the email address and still appearing that message.

If you have not already, re-enter you details again and check you don't have any invalid characters or spaces. Invalid characters or spaces is the most common cause of the BAD_INPUT_ERROR message.

If that doesn't help try switching on debugging in the module and check the debug information in the error log for any invalid characters or spaces in the request.