ok maybe i understand what happened.
i think it crashed during the installation because it made a select all from items table, but since I come from an old site which held 115k ads and i imported them all at once into osclass, the plugin made a select all of all those ads and only managed to create 65k entries in the payments_publish table. so it either crashed for memory consumption or execution time out, i got to check that.
maybe the install procedure should be optimized to take into consideration the case of sites holding a lot of classifieds.