I have a wpmu site set up. one of my customers on the set

Hi, I have a wpmu site set up. one of my customers on the set up is having issues with editing posts…… what is strange is it is not every post just some….. we have tried everything from turning off all the plugins to changing themes and it is not working.

another problem we are having is, we can edit most of the other posts, but once we do an update, then click publish or update, the page goes blank. the only way we know any updates have happened is if we visit the site.

the other problem we are having is we are not able to permanently delete any thing we put in the trash. Any help you can give me on this would be very highly appreciated.

Thanks for your time.

Tony V