This may be a issue for any ISP...
I was getting real high latency, which was only apparent when playing games. It turns out that Dropbox camera/file upload can kill your internet connection, and I was seeing pings to my ISP gateway jumping from 15ms to 1500ms.
I noticed that this is due to Dropbox upload, which can be throttled on PC/Mac, but there is no such option for mobile apps.
Just so you know!
Full thread here: http://community.vodafone.co.nz/t5/Broadband-services/Broadband-High-Latency-Blockhouse-Bay/m-p/202317/highlight/false#M18804