Converted reports run slow

I have recently converted a database from Access 2.0 to Access 2000 and I
have a set (5) of reports that all work almost exactly the same - based on
the same query too. They all run really quick, but then I had to make a
minor change to 1 of them, and now it runs SO slow. I took 1 of the other
quick reports and copied it to my slow report, and it was quick, until I went
into the Design - making no changes whatsoever - and hit the Save. I haven't
tried totally recreating this report to see if that will make it improve, as
I see that as a last resort. Where should I look for a solution to this?