Got a report from a Linux user of inability to reach Bugzilla in Opera; I was able to reproduce this on my Mac.
Some of our side sites such as:
are advertising IPv6 addresses in DNS. In at least some circumstances, Opera appears to attempt to connect over IPv6 even if there isn't a functional IPv6 link to the outside internet. (On my Mac, the only working IPv6 around is for the ZeroConf .local network.) The connection fails, but Opera just sort of stalls and gets confused instead of something sensible like falling back to IPv4.
Confirmed problem in Opera 9.54 and 9.63 for Mac.
This newsgroup post describes the issue on WinXP with IPv6 enabled:
Would be good if we can make sure this is getting fixed upstream in Opera, or have some standard workaround directions we can provide.