Sorry to hear about that, too, DavidST. I rarely use a computer/laptop/tablet for filmstruck for any of the services I subscribe to, but I have not experienced any issues with Firefox using both WIndows 7 and 10. I also have fast wireless and frequently use an ethernet connection for work reasons, so I have an optimal environment.
I have a feeling there may be issues with Vista. Granted, this was not a successful operating system. General support by Microsoft has ended for Vista, and extended supported will conclude in April.
With that said, the only criteria Filmstruck lists is browser versions and the latest version of Flash. If you have the correct versions of both, and you cleared your cache, then it should work (or Filmstruck should be able figure it out). Lack of memory or bandwidth would result in buffering issues, what you're describing is something different (leading back to Vista). I bet they'll start listing OS requirements in the future.
I'm sure there are hiccups with a newer service that doesn't occur with Netflix and Hulu. That certainly doesn't make it OK, nor does it help one's frustration. I certainly would lack patience as well, and I work in technology (and run a number of diagnostics before I go to support). One reaches a point where it isn't worth the frustration.
I certainly wouldn't buy a device for one supplemental service. I just happened to use a number of apps, so adding Filmstruck (after having an extended free period due to Beta testing) made the purchase easy for me.
Frankly, I am not sure how sales have been. I love it, but I wonder if the content is more for a cult following.