microsoft word document name or path not valid (1 Viewer)

[s.m.i.t.h]

sometimes when i download documents of the usyd blackboard site and i try to open them they wont open instead a message comes up 'the doc name or path is not valid .....etc' i hav tried renaming the doc and adding .doc at the end but it still wont open?

please help!

 

[s.m.i.t.h]

yes ive saved it then opened it
still same prob