When I tried out the .90rc version it installed a : -rwxr-xr-x 1 root root 1164073 Nov 4 11:31 libclamav.so.1.0.32 When I changed back to 0.88.6 the Redhat, and FC5 OS both OS's linked the libclamav.so.1 to the highest version of libclamav.so.1 which was libclamav.so.1.0.32. Maybe there is some prompting or checking that confuses this on linux but not on Solaris. So it looked like the following when I upgraded to 0.88.7 lrwxrwxrwx 1 root root 19 Dec 12 10:43 libclamav.so ->libclamav.so.1.0.19 lrwxrwxrwx 1 root root 19 Dec 12 10:43 libclamav.so.1 ->libclamav.so.1.0.32 -rwxr-xr-x 1 root root 894335 Oct 16 12:41 libclamav.so.1.0.17 -rwxr-xr-x 1 root root 894495 Nov 14 14:24 libclamav.so.1.0.18 -rwxr-xr-x 1 root root 896151 Dec 12 10:43 libclamav.so.1.0.19 -rwxr-xr-x 1 root root 1164073 Nov 4 11:31 libclamav.so.1.0.32 Maybe there is some prompting or checking that confuses this on linux but not on Solaris. So it looked like the following when I upgraded to 0.88.7 lrwxrwxrwx 1 root root 19 Dec 12 10:43 libclamav.so ->libclamav.so.1.0.19 lrwxrwxrwx 1 root root 19 Dec 12 10:43 libclamav.so.1 ->libclamav.so.1.0.32 -rwxr-xr-x 1 root root 894335 Oct 16 12:41 libclamav.so.1.0.17 -rwxr-xr-x 1 root root 894495 Nov 14 14:24 libclamav.so.1.0.18 -rwxr-xr-x 1 root root 896151 Dec 12 10:43 libclamav.so.1.0.19 -rwxr-xr-x 1 root root 1164073 Nov 4 11:31 libclamav.so.1.0.32 That was the problem. Maybe you can add that to the FAQ to make sure the libclamav.so and libclamav.so.1 are pointing to the correct version after the install: Should be: lrwxrwxrwx 1 root root 19 Dec 12 10:43 libclamav.so -> libclamav.so.1.0.19 lrwxrwxrwx 1 root root 19 Dec 13 10:06 libclamav.so.1 -> libclamav.so.1.0.19 -rwxr-xr-x 1 root root 894335 Oct 16 12:41 libclamav.so.1.0.17 -rwxr-xr-x 1 root root 894495 Nov 14 14:24 libclamav.so.1.0.18 -rwxr-xr-x 1 root root 896151 Dec 12 10:43 libclamav.so.1.0.19 I removed the libclamav.so.1.0.32 so this dosen't happen again.