are you going to m.youtube.com? if not try that, if you are going there try going to blueapple.mobi, if you know the name of the video you can just download it onto your phone and not have to bother with waiting on buffering times and other trash like that.
for the slacker app; I'm totally taking a guess at this one, anyone else please feel free to jump in on this one. I would back up your micro SD card to your computer and format it. it kind of sound (to me anyway) like it has lost the file structure and it is try to save to a fold that either does not exist or is corrupt of what have you, so I say, Delete that slacker app, Format the card (after backing it up first!) and re-install.
hopefully you'll be all good again!