fail to categorize a product

i able to add product in specific catagory in computer A but can not do that in computer B.
in computer A, after i add a product, select a catagory and click OK, it always fail me . the box to add catagory is not totaly jump out.(refer pic 1)
in computer B,after i add a product, select a catagory and click OK, the box will disappear. the product succesful put in the catagory.
do you have any ideal why this happen ?
i attached a pic about the fail infor.pic 2

i update to ver 1.4.0, but same problem stil happen.
i arrange my steps in pdf for your reverence.( these steps done in previous ver.)
the fail message to be same.

On IE , XP can add product in category.
On IE, vista business can not add product in catagory

IE ,Win XP, ver 8.0.6001.18702 can add product in catagory
IE, Win Vista business, ver 7.0.6000.16982 can not add product in catagory

i update my IE to ver 8. so far, every thing is going well.
i think the problem solve.