I\'m on BOINC 4.19. I keep getting messages like this when it tries to upload:

climateprediction.net - 2005-07-06 19:50:59 - Sending request to scheduler: http://climateapps2.oucs.ox.ac.uk/cpdnboinc_cgi/cgi

--- - 2005-07-06 19:51:00 - Can\'t resolve hostname climateapps2.oucs.ox.ac.uk (valid name, no data record of requested type)

climateprediction.net - 2005-07-06 19:51:00 - scheduler init_op_project to http://climateapps2.oucs.ox.ac.uk/cpdnboinc_cgi/cgi failed, error -113

climateprediction.net - 2005-07-06 19:51:00 - Deferring communication with project for 1 minutes and 0 seconds

And occasionally;

climateprediction.net - 2005-07-06 23:24:03 - Sending request to scheduler: http://climateapps2.oucs.ox.ac.uk/cpdnboinc_cgi/cgi
--- - 2005-07-06 23:24:03 - Can\'t resolve hostname climateapps2.oucs.ox.ac.uk (valid name, no data record of requested type)
climateprediction.net - 2005-07-06 23:24:03 - scheduler init_op_project to http://climateapps2.oucs.ox.ac.uk/cpdnboinc_cgi/cgi failed, error -113
climateprediction.net - 2005-07-06 23:24:03 - Deferring communication with project for 1 minutes and 0 seconds
--- - 2005-07-06 23:25:03 - Can\'t resolve hostname climateprediction.net (valid name, no data record of requested type)
climateprediction.net - 2005-07-06 23:25:03 - Couldn\'t read master page for climateprediction.net: error -113
climateprediction.net - 2005-07-06 23:25:03 - Master file fetch failed
climateprediction.net - 2005-07-06 23:25:03 - Deferring communication with project for 1 minutes and 0 seconds

As I recall, this is saying that BOINC can't access the servers, but in reality, it can't get to the net. (error 113)
It's just that BOINC isn't smart enough to know this; only that it's not getting a response from the other end.

Does this mean my PC is working pointlessly?

It means that it is producing data, which will eventually spill all over the floor, uless you unblock the output pipe.
In other words, find out why BOINC can't access the net. Change of setting in: firewall, proxy server, LAN, etc? Virus / trojan infection, which has altered your settings?
CPDN will happily crunch away, storing data on your hard disk until: you run out of disk space; it crashes; you give up on the problem.
BOINC will keep trying to access the servers, gradually increasing the 'time to next attempt' until it is waiting weeks to the next attempt.

As Les said, that is the output in the Messages tab of the BOINC GUI when BOINC can't reach the net. I have the cable pulled on one Windows PC right now and those are the exact messages that are being logged.