I have always had problems when using the phone or using on line chat to contact virgin support. When they ask for 3 characters of my password, the check always fails. I eventually get through after answering other security questions.
I had to call virgin today about something else and took the opportunity to ask about these password verification issues. I pointed out that I was currently logged on to virgin media and TV go using my media account email/password combination. What they told me surprised me. They said that I also have another "account" password which is used when contacting virgin. This is clearly different to my media account password. The agent was able to synchronise the 2 passwords to make them thethe s. I did point out that the was a bit confusing - I cannot find any mention of this second password on any of the FAQs etc. I asked how you were supposed to change this password - you cannot do it online - the agent said I would have to phone virign.
So if you are experiencing the same password verification problems as me, this may be why.