If you have not tried Chrome give that a go however I suspect you already have tried everything. If you give faults a call they can look into this for you and generally will raise it as an issue and resolve it for you.
I would avoid peak times early evening. i am sure they will be able to look after you.
Has this post helped you out? say thanks by clicking on the Kudos Star. I work for Virgin Media - but all opinions posted here are my own