SETI@home - 2004-07-10 22:23:12 - Sending request to scheduler: http://setiboinc.ssl.berkeley.edu/sah_cgi/cgi
SETI@home - 2004-07-10 22:23:16 - Scheduler RPC to http://setiboinc.ssl.berkeley.edu/sah_cgi/cgi failed
SETI@home - 2004-07-10 22:25:21 - No schedulers responded
for the last 3 weeks
beta tester no problem
boinc_3.19_windows_intelx86.exe
WinXP
pc 1 Number of times client has contacted server 260
pc 2 Number of times client has contacted server 109
pc 3 Number of times client has contacted server 154

The URL in those messages is the old scheduler URL. This is one of those cases where the "10 failures" mentioned on the Project frontpage will occur. It's easy to fix, though. DON"T DETACH/RE-ATTACH as they suggest!
Go to your Projects tab, right-click the SETI project, and select "Update".
Check the Messages tab. If it says it failed, then repeat.
Depending on how many times it has already failed for THIS PARTICULAR REASON (SINCE they made this change), you may have to repeat this up to 10 or 11 times. (It worked for me on the 12th attempt).
When it finally works, you will notice that the scheduler URL in the messages is different: it starts with "setiboincdata" now.