I could bet you're connecting on a Acer laptop... I've meet 1 other avatar that had same issue than I, and this solution helped...
1 - log in
2 - go me, preferences
3 - set cookies/temp folders to a different folder
4 - aply, close, upload
I created 2 esktop folders, sltemp1 and sltemp2 so I switch easy between the two everytime I log. I need to do this everytime I want to upload after logging. If I disconnect and log again, will have to do it again.
Its a pain in the *** but it works, and that way you'll be able to do uploads. Try it hope it fixes.