My lovely tester (aka wife) has occasional troubles opening her yahoo inbox. I wasn't able to find it in the logs until now. She had problems with 7.460 and 7.470. (I had web proxy off for 7.450) After a few attempts, then it will work for a while.
Attached are logs showing the block followed by the pass.
Proxy settings are: Transparent (full mode not checked), no AV, URL filter is Allow with no categories selected, block spyware infection/communication is checked. Always allow entry is "^https?://.*yahoo.com". Bypass content scanning for streaming content and http caching is checked.
