OSCommerce - No input file specified

Need to resolve a problem that just arose with error message "No input file specified" in existing OsCommerce installation. Message only occurs in OSC Admin. and only happens when clicking on Configuration and Catalog in Admin. All other menu items - Modules, Customers, Locations, Localization, Reports, Tools don't bring up this error message. Shopping cart on web side is also OK. OSC installation was recently upgraded to operate with PHP5 (by a Freelancer provider) but not sure whether this problem happened only after this work was done or later.