Those messages indicate that the BOINC client on you machine tried to contact the WCG servers and download those files but wasn't able to. Normally, the BOINC client will request new work from the servers when it is needed. Part of the is the files that make up that new work. Usually all the files get downloaded just fine. However, sometimes things happen during that process - the servers could go down, the process on the servers that sends the files could not be running at that moment, your internet connection could have dropped, any number of things. Nice thing is though that once the retry/backoff times run down, the BOINC client will try again to download those files until it succeeds. Usually, there's nothing to worry about. If you look at the event log (under Tools), you may see some messages that will give some indication of where the problem was. If this happened just before your post, you may have happened to hit one of the few times during the day when some process is running that needs to have the process that sends files out wait until it finishes first.

I also noticed this a few times today. It cleared itself up as the servers caught up with the loads. Just let it run and they will upload eventually. And, I expect the same situation for downloads.

Some security software [and proxies] mangle the security certificate data during transmission [WCG requires secure handshaking]. This often when a software update has gone just before that [the signature files or the engine itself]. This can happen silently [I've blocked that except for the signature file refreshing].