Also running 6.0.8 on Ubuntu 8.04 64 bit. I checked my own server after reading your post, and I'm seeing the same thing. Auto-complete works fine, GAL searches return no results. Is there another log that may be more helpful than mailbox.log? I'm not getting much help from it.
Code:
2010-09-15 22:32:16,327 INFO [btpool0-8060://localhost/service/soap/SearchGalRequest] [name=me@mail.com;mid=5;oip=my ip address;ua=zclient/6.0.8_GA_2661;] soap - SearchGalRequest
2010-09-15 22:32:16,428 INFO [btpool0-8060://localhost/service/soap/SearchGalRequest] [name=me@mail.com;mid=5;oip=my ip address;ua=zclient/6.0.8_GA_2661;] SoapEngine - handler exception