When you upload many images under your google account the time is longer and refresing of upload gui is slow.
You can test your user interface to see how MiB is uploading to google server.
See the next linux command.
$ watch -d 'ifconfig | grep MiB | grep "TX bytes"' And result is something like this:
Every 2.0s: ifconfig | grep MiB | grep "TX bytes" Thu May 2 22:44:09 2013
RX bytes:15625675 (14.9 MiB) TX bytes:184506104 (175.9 MiB) 