assign a keyword to multiple (90) images in a collection

I tried selecting them all and checking the keyword in the keyword paneldu. The clock spins and it seems as if the keyword is checked but then when I check an individual file, the keyword is not checked. Even if I try to assign a keyword to each file one at a time (VERY TEDIOUS), the clock spins and it seems to assign the keyword but then when I go back and check it is no longer assigned. What is going on???

Thank you