Unable to upload photos from iPhone to Facebook

I have a 3GS iPhone (4.2.1). I used to be able to upload photos from my Camera Roll or Albums onto Facebook. But in the past couple of months, I cannot do that. I get a message saying Photo cannot be uploaded at this time, do you want to save it, dont save, cancel. But it never happens!
So I have to email the photo to my computer and then put it on Facebook that way.
Any ideas how I can rectify this problem?
iMac G4, MacBook Mac OS X (10.5.7) 8GB iPhone, 3GS (32G) iPhone