Clinton has had years to cover up this episode. And as the many, many Clinton scandals have taught us time and time again, it's not what you know, it's what you can prove in court.
If people won't talk out of fear for themselves or their families, if necessary witnesses are dead, if documentation is missing or has been shreaded, well...it's just talk...or shall we say, partisan politics. And seriously, Clinton has a willing and able, anti-Bush media on his side to spin anything and everything whatever way their talking points tell them to.
Consider...Sandy Berger hides LOTS of classified documents in his sox and underwear and it's just Sandy being SLOPPY! And the press actually reports this with a straight face!!!
Moreover, even if there was no direct evidence, if there was suspicion, can you really see Rummy or Ashcroft or Ridge refusing to reopen the investigation if there was the slightest doubt in their mind that AQ might have been involved? If for no other reason than to get further leads and evidence, they would have re-opened the investigation. But they didn't. We can't have it both ways: either the report is right, and Bush has no reason to investigate, or the report is a lie and Bush is covering up too.