Sophos 4.78 for AIX 5.2 not found?

We are using unmanaged Sophos on AIX5.2.

According to your website AIX 5.2 should be supported until 2013.

However, we cannot download Sophos 4.78 for AIX 5.2 from web site.

The AIX version just work for AIX 5.3+, not work on AIX 5.2.

Any idea?

Errow msg of running Sophos 4.78 on AIX 5.2.

# /usr/local/bin/sweep -v

exec(): 0509-036 Cannot load program /usr/local/bin/sweep because of the following errors:

        0509-130 Symbol resolution failed for sweep because:

        0509-136   Symbol __pth_init (number 85) is not exported from

                   dependent module /usr/lib/libpthreads.a(shr_xpg5.o).

        0509-136   Symbol __pthread (number 86) is not exported from

                   dependent module /usr/lib/libpthreads.a(shr_xpg5.o).

        0509-192 Examine .loader section symbols with the

                 'dump -Tv' command.

Thanks!!