php5 and post-thumb plugin

Hello,
my hosting went from php4 to php5 and for some odd reason, the configuration page of Post-Thumb revisited plugin has diseparead. When I try to go directly to it, I’ve got a 500 error. Somebody has an explanation (I did reinstall the plugin-go back to php4-the page is here again-change to php5 again-no more page).