I have found an issue that my PS3 is disconnected from the PS3 Media server when any downloads finish from the Playstation Network. This just started happening last week (Mar. 22nd 2011) when I was downloading demo's and videos from the Tuesday update. (There was a firmware update recently wasn't there? Might be from that)
I'm using my wired network to a quad core desktop AMD PC running Win 7, and has had 0 issues with streaming otherwise. The videos being played are not being transcoded, and the specific error is:
This content cannot be played.
My PS3 media server is the latest version: 1.20.412
Every time this error has come up it coincides with a download completing, every time without fail.