Computor problem with secure sites??..please help ASAP

[PinkChick]

cant can onto online banking, ebay (to pay or ask question) or anything that is deemed secure..it says could be caused by firewall settings but the only firewall we have was 'with' the computor?
we have avg ant virus, would this be causing the prob?..please help..need to order new contracts and lots of things and cant do any

the settings must be set to high can you get into it and lower them?

dont now how too? its just 'happend'?, we didnt re set them it just chnged?????will ask dp if he knows how to get into it?

still not sorted..dont know what else we're looking for to sort this out, does anyone have any ideas???

would being with ntl make any difference as they have just changed to virgin mmedia and our b.band is with them?????????

anyone???????????