I've been doing a little CPU crunching on NFS@Home with 2 logical cores for awhile now and it's unfortunate to report that its task seems to be punctured with quite a fair share of "Error while computing" issues. In order to sidestep it, just select to perform lasievef application only but the computer machine in question must be equipped with a lot of RAM perhaps, at least 8GB. So, the step-by-step procedure to crunch it is as follows;-
 
1. Create an account at NFS@Home.
2. Join our team.
3. Navigate from NFS@Home Preferences until Edit NFS@Home Preferences, just select "lasievef - occasionally used for huge factorizations, uses up to 1 GB memory" only and nothing else.
4. Ensure that "If no work for selected applications is available, accept work from other applications?" are UNtick and then, left-click "Update preferences" button.
5. Left-click "Add project or account manager..." under Tools in BOINC Manager v6.12.34 and then, left-click "Next >" button.
6. Select "NFS@home" with your mouse from the "Choose a project" window panel and then, left-click "Next >" button.
7. Just fill up your email address and choose & confirm your password on the "Identify your account" window panel and then, left-click "Next >" button.
8. Finally, left-click "Finish" button.
 
Note: Our team has a total credit of 32804 and is rank #213 while its DC-Vault score is ~5931pts.

AB Was Here... 

I've better than the previous good news to share!
 
Under VirtualBox 4.1.4 + Ubuntu 10.10 (with the latest patch update) hosted on a Windows 7 (Win7) Ultimate SP1 64-bit o/s machine (see my siggy for rig CPU-Z), lasievef task chews up ~475MB of RAM and completes within 40mins. Therefore, I can afford to run eight (8) instances of lasievef application now instead of just two (2) previously.
 
So, it takes less RAM by ~1.3MB and save up to 20mins per lasievef task to crunch as compared to on purely Win7 platform.

Unfortunately, Leiden Classical encounters "Compute error" (but done its job within 35mins however I'll try the latest builds of BOINC Manager 7.0.23, VirtualBox 4.1.12 & Ubuntu 11.10 to confirm later) as follows;-
 
stderr out

<core_client_version>6.12.34</core_client_version>
<![CDATA[
<stderr_txt>
Unrecognized XML in parse_init_data_file: userid
Skipping: 0
Skipping: /userid
Unrecognized XML in parse_init_data_file: teamid
Skipping: 0
Skipping: /teamid
Unrecognized XML in parse_init_data_file: hostid
Skipping: 95852
Skipping: /hostid
Unrecognized XML in parse_init_data_file: result_name
Skipping: wu_78596477_1332919788_25171_1
Skipping: /result_name
Unrecognized XML in parse_init_data_file: starting_elapsed_time
Skipping: 0.000000
Skipping: /starting_elapsed_time
Unrecognized XML in parse_init_data_file: computation_deadline
Skipping: 1334127274.136000
Skipping: /computation_deadline
Unrecognized XML in GLOBAL_PREFS::parse_override: mod_time
Skipping: /mod_time
Unrecognized XML in GLOBAL_PREFS::parse_override: run_gpu_if_user_active
Skipping: 1
Skipping: /run_gpu_if_user_active
Unrecognized XML in GLOBAL_PREFS::parse_override: suspend_cpu_usage
Skipping: 0.000000
Skipping: /suspend_cpu_usage
Unrecognized XML in GLOBAL_PREFS::parse_override: max_ncpus_pct
Skipping: 75.000000
Skipping: /max_ncpus_pct
Unrecognized XML in GLOBAL_PREFS::parse_override: daily_xfer_limit_mb
Skipping: 0.000000
Skipping: /daily_xfer_limit_mb
Unrecognized XML in GLOBAL_PREFS::parse_override: daily_xfer_period_days
Skipping: 0
Skipping: /daily_xfer_period_days

</stderr_txt>
<message>
upload failure: <file_xfer_error>
  <file_name>wu_78596477_1332919788_25171_1_1</file_name>
  <error_code>-161</error_code>
</file_xfer_error>

</message>
]]>