I experience this too, but it is only limited to SSL sites with unknown (custom created) certificates. The exact errors I am seeing in my SSL webserver log files are:
[03/Nov/2001 13:26:32 10240] [info] Connection to child 19 established (server default:443, client x.x.x.x)
[03/Nov/2001 13:26:32 10240] [info] Seeding PRNG with 1160 bytes of entropy
[03/Nov/2001 13:26:32 10240] [error] SSL handshake failed (server default:443, client x.x.x.x) (OpenSSL library error follows)
[03/Nov/2001 13:26:32 10240] [error] OpenSSL: error:14094416
SL routines
SL3_READ_BYTES:sslv3 alert certificate unknown
Note: x.x.x.x is my client IP