First thanks for the great plugin. It took some doing, but I've finally got the thing working! Updated to PHP5, then fought with the 'Unable to verify POST vars' error, finally solved that (stupid PayPal sandbox!), then encountered the 'link you have used to enter the PayPal system is invalid' error, discovered I had forgotten to include openSSL when upgrading PHP, now finally it now works!
However I have a new issue :) s2member appears to be inserting this stylesheet on each page:
<link rel='stylesheet' id='ws-plugin--s2member-css' href='http://my-church.net/wordpress/?ws_plugin__s2member_css=1&qcABC=1&ver=3.5.6-921517325' type='text/css' media='all' />
But this conflicts with the stylesheet for SimplePress, so the fonts are too big and the background is all wrong. This only occurs on the SimplePress section of my site, everything else looks fine. Any ideas how I can override this (without going into SimplePress and changing all the CSS classes!). I can't even tell what the s2member CSS is doing.