Calculating certain files take a long time to move/access

On certain files that I have downloaded (usually PDF but then I work with PDF's a lot) when I try to access them in any way (check properties, open them, move them or trash them) they take a long time to open like 30-45 seconds. The size of the files can be very small 45-100kb but even much larger files can take the same amount of time. Size doesn't seem to affect the problem. The entire time the dialogue box shows "calculating" .

Once I have accessed them once doing it subsequently is always normal.

Any ideas would be appreciated.

Thx,
Ned

I use FoxIt Reader but I have solved the problem (at least for now) by removing "InstallShield Update Service Update Manager" a service which is not necessary.

Thx for replying!
Ned