Re-checked the logs and found the following:
[Thu Jul 25 09:46:42 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:46:42 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:46:42 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 0 to 8 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:46:43 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:46:43 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:46:50 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:46:50 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:46:51 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:46:51 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:47:01 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:47:02 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:47:02 2013] [debug] mod_headers.c(756): headers: ap_headers_output_filter()
[Thu Jul 25 09:47:02 2013] [debug] mod_deflate.c(615): [client 203.217.28.248] Zlib: Compressed 29 to 29 : URL /prestashop/install/index.php, referer: <referer>
[Thu Jul 25 09:47:05 2013] [notice] child pid 1982 exit signal Segmentation fault (11)
*** glibc detected *** /usr/sbin/apache2: free(): invalid pointer: 0x00007fd0c39b90fb ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7eb96)[0x7fd0c7c5db96]
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0(CRYPTO_free+0x1d)[0x7fd0c35f83ed]
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0(sk_free+0x17)[0x7fd0c3680437]
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0(+0x62d49)[0x7fd0c35f9d49]
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0(BIO_free+0x79)[0x7fd0c3677169]
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0(BIO_free_all+0x24)[0x7fd0c3677af4]
/lib/x86_64-linux-gnu/libssl.so.1.0.0(SSL_free+0x8b)[0x7fd0c39abc7b]
/usr/lib/apache2/modules/libphp5.so(+0xf9c1c)[0x7fd0c4777c1c]
/usr/lib/apache2/modules/libphp5.so(_php_stream_free+0xd2)[0x7fd0c4965aa2]
/usr/lib/apache2/modules/libphp5.so(+0x262efc)[0x7fd0c48e0efc]
/usr/lib/apache2/modules/libphp5.so(+0x1a856e)[0x7fd0c482656e]
/usr/lib/apache2/modules/libphp5.so(+0x3989ad)[0x7fd0c4a169ad]
/usr/lib/apache2/modules/libphp5.so(execute+0x1fb)[0x7fd0c49c751b]
/usr/lib/apache2/modules/libphp5.so(zend_execute_scripts+0x130)[0x7fd0c49a2a80]
/usr/lib/apache2/modules/libphp5.so(php_execute_script+0x1d3)[0x7fd0c494f0f3]
/usr/lib/apache2/modules/libphp5.so(+0x3b3f8d)[0x7fd0c4a31f8d]
/usr/sbin/apache2(ap_run_handler+0x48)[0x7fd0c8aba508]
/usr/sbin/apache2(ap_invoke_handler+0xce)[0x7fd0c8aba97e]
/usr/sbin/apache2(ap_process_request+0x1a0)[0x7fd0c8aca570]
/usr/sbin/apache2(+0x4e398)[0x7fd0c8ac7398]
I'm not sure this will help a lot.
However, i've looked through the source code and I would expect there to be some output from the application, I've also tried this http://www.prestasho...1457-error-log/ to no avail.
Interestingly, when I try to access the shop after the failed partial installation, it still comes up. But when I try to login to the admin interface, it fails with a 'parerserror' message.
Any more ideas?