then the theme you're using needs to have its code changed (or the plugin you're using is outdated) . Hard to say without seeing it, but that's the exact description of the behavior of the FLV player not loaded in the page. As a matter of fact I had the same problem a couple weeks ago just because I forgot to upload the player, did it and it worked like a charm. Check out if there's some relative path that has changed or if your plugins are updated and working on 2.8.x (most plugins still aren't). If the problem is the plugin, your best bet is to downgrade to 2.7 and wait til the plugins are updated to work with 2.8. If the problem relies on the theme (for what you say, I'm quite sure that's where the problem is), just try to find out where's the part that brings the problem. As I said, without seeing the code it's impossible to say something accurate.
On a side note: most video themes I've seen are extremely weak and badly coded. If you feel confident and want to edit your theme so it ALWAYS work, do the following:
1) in your theme, replace the code for your video/s with the following:
Code:
<object width="640" height="360" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0">
<param name="quality" value="high"> <param name="wmode" value="transparent">
<param name="movie" value="http://geekfile.googlepages.com/flvplay.swf">
<param name="FlashVars" value="&streamName=<?php echo get_post_meta($post->ID, "YOUR_CUSTOM_FIELD", $single = true); ?>&skinName=http://geekfile.googlepages.com/flvskin&autoPlay=true&autoRewind=true">
<embed width="640" height="360" flashvars="&streamName=<?php echo get_post_meta($post->ID, "YOUR_CUSTOM_FIELD", $single = true); ?>&autoPlay=true&autoRewind=true&skinName=http://geekfile.googlepages.com/flvskin" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" src="http://geekfile.googlepages.com/flvplay.swf" wmode="transparent">
</embed>
</object>
2) be happy
the above can be modified to use JWPlayer and FlowPlayer with just a couple changes. I'm not sure if you can use dynamically loaded video with OS FLV (never tested it), but at most you'll need some editing.
PS: in the code above, you OBVIOUSLY need to edit some data, like size and maybe some flashvar or wmode