I'm afraid that tasks are erroring out right as they begin, on my 64-bit Ubuntu rig running Gibbs sampler v0.14... Any idea what might be wrong?

My Windows machine is working just fine with Gibbs sampler v0.18 though, so that's good.

BOINC is sending many 32-bit v0.14 tasks that are incompatible with your 64-bit Linux. The correct version v0.13 tasks for your 64-bit Linux are completing successfully on your computer.

This is a design error of BOINC. It has been mentioned in other threads.

I see. So there's nothing to be done but wait for a bug fix?

Perhaps you could "update your gcc" http://dnahome.cs.rpi.edu/dna/forum_thread.php?id=87&nowrap=true#659
That's Linux talk, I think it means update your operating system.

I remember when doing QMC in 64-bit Linux you had to add ia32-libs package plus some others to allow processing the QMC 32-bit Linux application. Those more familiar with Linux may be able to answer more knowledgably about this.
The Dotsch/UX Linux I use for BOINC so far has had no trouble processing 32-bit BOINC applications.

Another way is to use an app_info.xml file which should prevent BOINC from sending 32-bit tasks. I do not know how to do this for this project.

Getting numerous errors or aborting tasks should possibly be avoided on any project using the BOINC assigned credit scheme. I'm not sure but it may affect the amount of credit granted. If any component of the scheme is based on the BOINC benchmark then a higher benchmark relative to task runtime is also desirable for you and your wingman. This may be advantageous to those with hyper threading CPUs and also CPUs with turbo boost features.

I'm not sure why you are using both 64bit and 32bit 0.17 app versions for both Win and Linux, or if it would help to separate them by version number.
For example,
Win x86 Version 0.17, x64 Version 0.18
32bit Linux 0.19, 64bit Linux 0.20

I can't see anything on the tasks properties to indicate whether they are either x86 or x64. Might be useful.

... Another way is to use an app_info.xml file which should prevent BOINC from sending 32-bit tasks. I do not know how to do this for this project...

Finally I got the app_info.xml's working for Windows and Linux x64! :-)))
____________
Grrrrrrrrreetings from the Lazy Cat...

Well go on then! Post them for us lazy bones! ;)
____________
Dublin, CA
Team SETI.USA

And there I though I was a lazy cat... *big grin*
So here we go for Windows x64:

<app_info>

<app>
<name>Gibbs</name>
<user_friendly_name>Gibbs sampler</user_friendly_name>
</app>

<file_info>
<name>Gibbs_0.18_windows_x86_64.exe</name>
<executable/>
</file_info>

<file_info>
<name>mtub_NC_000962_intergenic.2.43X.fa</name>
<sticky/>
</file_info>

<app_version>
<app_name>Gibbs</app_name>
<version_num>18</version_num>
<file_ref>
<file_name>Gibbs_0.18_windows_x86_64.exe</file_name>
<main_program/>
</file_ref>
</app_version>

</app_info>

<app_info>

<app>
<name>Gibbs</name>
<user_friendly_name>Gibbs sampler</user_friendly_name>
</app>

<file_info>
<name>Gibbs_0.18_x86_64-pc-linux-gnu</name>
<executable/>
</file_info>

<file_info>
<name>mtub_NC_000962_intergenic.2.43X.fa</name>
<sticky/>
</file_info>

<app_version>
<app_name>Gibbs</app_name>
<version_num>18</version_num>
<file_ref>
<file_name>Gibbs_0.18_x86_64-pc-linux-gnu</file_name>
<main_program/>
</file_ref>
</app_version>

</app_info>

Hehe, no... only 3 boxes in total - I should be able to manage that. *grin*
____________
Grrrrrrrrreetings from the Lazy Cat...

It looks like the project-side fix worked. So the need is gone, I think.
____________
Dublin, CA
Team SETI.USA