I can now provide details about why build 693 was causing problems for me. Hope it helps someone out there.
Starting with build 693, Roku changed the default minimum bandwidth to 250Kbps which is sensible because you would rarely want to play a video stream less than this. However, in this case I was creating my segmented HTTP streams using Wowza Media Server and Wowza, by default, marks the stream bandwidth in the .m3u8 as 64Kbps regardless of the actual bitrate as follows:
Thus my Wowza HTTP streams would not play. With Wowza, if you want to control the bandwidth reported in the .m3u8 file then you need to put a .smil file in the content directory similar to the following:
<video src="mp4:720p.sdp" system-bitrate="2200000"/>
<video src="mp4:ipad.sdp" system-bitrate="748000"/>
<video src="mp4:mobile.sdp" system-bitrate="200000"/>
This .smil file has three streams listed for adaptive streaming, but you could also have only one stream listed. As a side note, I believe that you will want to have highest bandwidth to lowest order in the .smil if you are doing adaptive.
Alternatively, you can modify the minimum bandwidth to a lower value so that the default Wowza bandwidth does not get in the way. Below is an example and I believe the value specified is in Kbps.
videoclip.minBandwidth = 20
Once I forced Wowza to put the correct bitrate in the .m3u8 or lowered the minBandwidth, the problem with build 693 not playing the stream is gone as expected. I have another issue with HD streams freezing on playback, but that will be the topic of another post.