maybe you just clicked "No new tasks" on the WCG in BOINC, or just have some tasks suspended

here's the initial part of client_state.xml :

<host_info>
<timezone>3600</timezone>
<domain_name>Home-iMac.local</domain_name>
<ip_addr>172.19.3.102</ip_addr>
<host_cpid>52ac871da828d208d4a17fabb299f651</host_cpid>
<p_ncpus>2</p_ncpus>
<p_vendor>GenuineIntel</p_vendor>
<p_model>Intel(R) Core(TM)2 Duo CPU E8235 @ 2.80GHz [x86 Family 6 Model 23 Stepping 6]</p_model>
<p_features>FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM SSE3 MON DSCPL VMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1</p_features>
<p_fpops>3271433086.269975</p_fpops>
<p_iops>11836480679.411167</p_iops>
<p_membw>1000000000.000000</p_membw>
<p_calculated>1232639003.694553</p_calculated>
<m_nbytes>4294967296.000000</m_nbytes>
<m_cache>1000000.000000</m_cache>
<m_swap>190256029696.000000</m_swap>
<d_total>499763888128.000000</d_total>
<d_free>189993885696.000000</d_free>
<os_name>Darwin</os_name>
<os_version>9.6.0</os_version>
<accelerators></accelerators>
</host_info>
<time_stats>
<on_frac>0.778926</on_frac>
<connected_frac>-1.000000</connected_frac>
<active_frac>0.733300</active_frac>
<cpu_efficiency>0.503643</cpu_efficiency>
<last_update>1232656107.247246</last_update>
</time_stats>
<net_stats>
<bwup>21440.361851</bwup>
<avg_up>496749.665680</avg_up>
<avg_time_up>1232653913.757462</avg_time_up>
<bwdown>1721002.667353</bwdown>
<avg_down>12724491.033595</avg_down>
<avg_time_down>1232648991.385741</avg_time_down>
</net_stats>

Here's the startup-log after modifying the client_state.xml as suggested :
Fri Jan 23 07:17:51 2009||Starting BOINC client version 6.2.18 for x86_64-apple-darwin
Fri Jan 23 07:17:51 2009||log flags: task, file_xfer, sched_ops
Fri Jan 23 07:17:51 2009||Libraries: libcurl/7.18.0 OpenSSL/0.9.7l zlib/1.2.3 c-ares/1.5.1
Fri Jan 23 07:17:51 2009||Data directory: /Library/Application Support/BOINC Data
Fri Jan 23 07:17:51 2009||Processor: 2 GenuineIntel Intel(R) Core(TM)2 Duo CPU E8235 @ 2.80GHz [x86 Family 6 Model 23 Stepping 6]
Fri Jan 23 07:17:51 2009||Processor features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM SSE3 MON DSCPL VMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1
Fri Jan 23 07:17:51 2009||OS: Darwin: 9.6.0
Fri Jan 23 07:17:51 2009||Memory: 4.00 GB physical, 174.96 GB virtual
Fri Jan 23 07:17:51 2009||Disk: 465.44 GB total, 174.72 GB free
Fri Jan 23 07:17:51 2009||Local time is UTC +1 hours
Fri Jan 23 07:17:51 2009||No coprocessors
Fri Jan 23 07:17:51 2009|rosetta@home|URL: http://boinc.bakerlab.org/rosetta/; Computer ID: 209026; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009|boincsimap|URL: http://boinc.bio.wzw.tum.de/boincsimap/; Computer ID: 57471; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009|Leiden Classical|URL: http://boinc.gorlaeus.net/; Computer ID: 50231; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009|climateprediction.net|URL: http://climateprediction.net/; Computer ID: 325638; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009|Einstein@Home|URL: http://einstein.phys.uwm.edu/; Computer ID: 610023; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009|SETI@home|URL: http://setiathome.berkeley.edu/; Computer ID: 1985761; location: home; project prefs: default
Fri Jan 23 07:17:51 2009|World Community Grid|URL: http://www.worldcommunitygrid.org/; Computer ID: 460892; location: (none); project prefs: default
Fri Jan 23 07:17:51 2009||General prefs: from World Community Grid (last modified 21-Jan-2009 21:53:15)
Fri Jan 23 07:17:51 2009||Host location: none
Fri Jan 23 07:17:51 2009||General prefs: using your defaults
Fri Jan 23 07:17:51 2009||Reading preferences override file
Fri Jan 23 07:17:51 2009||Preferences limit memory usage when active to 819.20MB
Fri Jan 23 07:17:51 2009||Preferences limit memory usage when idle to 3072.00MB
Fri Jan 23 07:17:51 2009||Preferences limit disk usage to 9.31GB
Fri Jan 23 07:17:51 2009|climateprediction.net|Restarting task hadsm3mh_km8w_006011476_6 using hadsm3mh version 604

Two tasks 'ready to report' appeared. After hitting update, I gotthe smae message as before:
Fri Jan 23 07:22:44 2009|boincsimap|Sending scheduler request: To fetch work. Requesting 3570 seconds of work, reporting 0 completed tasks
Fri Jan 23 07:22:49 2009|boincsimap|Scheduler request succeeded: got 0 new tasks
Fri Jan 23 07:23:39 2009|World Community Grid|Sending scheduler request: Requested by user. Requesting 0 seconds of work, reporting 2 completed tasks
Fri Jan 23 07:23:44 2009|World Community Grid|Scheduler request succeeded: got 0 new tasks

Very much possible it's a multi project debt balance, WCG owing too much time to the other project, thus the scheduler won't fetch work from WCG until it's debt has been reduced.

There is a third party tool to reset the long term debt called BOINC DV or something: http://boinc.berkeley.edu/addons.php

Discussed here: http://boinc.berkeley.edu/dev//forum_thread.php?id=1901&nowrap=true