Problems with paypal

HI!

I run a webshop using opencart 1.5.6.4 and a paypal plugin. For some of my customers when going through and ordering on the last step payment choosing paypal they just get back on the first page on the ordering page (fill in adress).

For some customers this works without any issues. I've tried all browsers and can't replicate it. The error seems random. Anyone know where i can find help on this?

Which PayPal module are you using and are there any errors in your error log?

It might also be helpful to post the site's address.