loads of errors after user decides not to pay for listing

[aoifa]

hi, received loads of errors after user decides not to pay for listing at "pay with paypal" stage.

if a user creates a listing, osclass creates the listing and admin is notified of new listing but if the user subsequently decides to break off and not proceed at the "pay with PayPal" page stage,  the following errors happened, 1) categories "broken", no sub-categories showing. 2) fatal error at admin log in in admin.php line 61. 3) upon opening site again about 5 or 6 different fatal errors appeared above the "normal" header and browser window closed

any idea anybody ?- will re-install osclass, but will leave off payment until solution suggested.

[design]

what payment plugin are you using? the paypal one does NOT work

we use the same theme, I have modified my payment plugin (with core changes) and everything works, if they back out of it the ad goes blocked.
that being said I only allow registered users and each listing must be self activated by the user before it will post.

[aoifa]

hi design, thanks for reply -
our 1st site is free as it is a "club-site" so no issue there.
was going to set up a 2nd site for "external" use and added a pay per post cost with" payment plugin" ( not PayPal plug in)
was testing the set up when this error occurred,
no modification done to plug-in - registered users only - no activation in settings
did not have time to re-install as yet, when I have I will try again.