Hi Holly,
Assuming, as you stated, you are not in FAP, and also assuming that you don't have any "conditions" affecting your connection: (are icons #1 & #2 both green)
(click on picture of larger image):
Then you may wish to try the following:
1st: It may be that you are trying to stream in "HD" and the system just can't keep up.
Try turning the resolution down to something less.
Streaming in HD takes an extreme amount of data to support.
2nd: In some cases turning off Web Acceleration for the duration of the operation may help.
On a Gen4 system system this is dome by clicking on the #3 icon in the picture above, that leads to the modems "advanced pages" and the select from the "menu" tree on the left as shown here:
and placing a checkmark in the box next to "disable Web Acceleration" the clicking the SUBMIT button.
Re-enable when you are done.
There are some people the claim their systems perform better disabled, however, I suggest you look at it not as an either/or condition but as a "switch" to be "toggled" to one setting or the other as conditions demand.