Two machines, both running 32bit Ubuntu 8.04, both running BOINC 6.4.5. Both can run memtest for days with no errors.
Neither machines throws errors on other projects.

First machine, a P4 2.4 (non-hyperthreading model)

Project Name: Human Proteome Folding - Phase 2
Created: 2/3/09
Name: mf378_00016

<core_client_version>6.4.5</core_client_version>
<![CDATA[
<message>
process exited with code 193 (0xc1, -63)
</message>
<stderr_txt>
SIGSEGV: segmentation violation
Stack trace (17 frames):
[0x8789e9f]
[0x877cfa4]
[0xb7f43420]
[0x843368e]
[0x8435b2e]
[0x84375a7]
[0x843a6b7]
[0x843c503]
[0x870e8e7]
[0x85e9ce8]
[0x85eb7c5]
[0x805cf24]
[0x8331f6b]
[0x83f3cdd]
[0x83f3f5c]
[0x87ed062]
[0x8048131]

Exiting...

</stderr_txt>
]]>


Project Name: Human Proteome Folding - Phase 2
Created: 2/2/09
Name: mf327_00087

<core_client_version>6.4.5</core_client_version>
<![CDATA[
<message>
process exited with code 193 (0xc1, -63)
</message>
<stderr_txt>
SIGSEGV: segmentation violation
Stack trace (13 frames):
[0x8789e9f]
[0x877cfa4]
[0xb7fed420]
[0x871633a]
[0x86678e9]
[0x870d848]
[0x826c508]
[0x805c7ec]
[0x8331f6b]
[0x83f3cdd]
[0x83f3f5c]
[0x87ed062]
[0x8048131]

Exiting...

</stderr_txt>
]]>


Project Name: Human Proteome Folding - Phase 2
Created: 2/2/09
Name: mf322_00013

<core_client_version>6.4.5</core_client_version>
<![CDATA[
<message>
process exited with code 193 (0xc1, -63)
</message>
<stderr_txt>
*** glibc detected *** free(): invalid next size (normal): 0x0a047408 ***
SIGABRT: abort called
Stack trace (24 frames):
[0x8789e9f]
[0x877cfa4]
[0xb7f6e420]
[0x87f4194]
[0x88096fb]
[0x880e831]
[0x880eb53]
[0x87dea29]
[0x87de87d]
[0x85fc846]
[0x864f5f7]
[0x8654774]
[0x866840e]
[0x8669dac]
[0x843b5d4]
[0x870e173]
[0x85e9c99]
[0x85eb7c5]
[0x805cf24]
[0x8331f6b]
[0x83f3cdd]
[0x83f3f5c]
[0x87ed062]
[0x8048131]

Exiting...

</stderr_txt>
]]>


Project Name: Human Proteome Folding - Phase 2
Created: 2/2/09
Name: mf310_00064

<core_client_version>6.4.5</core_client_version>
<![CDATA[
<message>
process exited with code 193 (0xc1, -63)
</message>
<stderr_txt>
SIGSEGV: segmentation violation
Stack trace (17 frames):
[0x8789e9f]
[0x877cfa4]
[0xb7fa2420]
[0x86087d3]
[0x865dc69]
[0x8661c05]
[0x84a9796]
[0x82a61de]
[0x82a6867]
[0x85e9583]
[0x85eb7c5]
[0x805cf24]
[0x8331f6b]
[0x83f3cdd]
[0x83f3f5c]
[0x87ed062]
[0x8048131]

Exiting...

</stderr_txt>
]]>


Project Name: Human Proteome Folding - Phase 2
Created: 2/1/09
Name: mf251_00004

<core_client_version>6.4.5</core_client_version>
<![CDATA[
<message>
process exited with code 193 (0xc1, -63)
</message>
<stderr_txt>
SIGSEGV: segmentation violation
Stack trace (13 frames):
[0x8789e9f]
[0x877cfa4]
[0xb7fd5420]
[0x871633a]
[0x86678e9]
[0x870d848]
[0x826b993]
[0x805c7ec]
[0x8331f6b]
[0x83f3cdd]
[0x83f3f5c]
[0x87ed062]
[0x8048131]

Exiting...

</stderr_txt>
]]>