[X4U] Safari download problem

[Michel Treisman]

Safari has stopped downloading documents from websites I visit.   
Mainly pdf but also html documents. I click on the document, a web  
page opens, the URL is selected, but after that nada, just a blank  
page. I am running 10.4.7 on a PowerBook.
  I have tried repairing permissions, running Applejack,  replacing  
the preference file, and my best guess now is that there is a plugin  
somewhere that is corrupted, but I can't find anything that looks  
right.  So what should I do now? Suggestions welcome.
Mike