Weird problem these last few days - NWOLB wouldn't run in either Firefox or Chrome - but was quite happy in Safari.
Had time this afternoon to have a look around for a solution - seems that NW have been setting some cookies that subsequently cause a 'security exception' when you try to start a banking session in Chrome or Firefox.
Easy solution is to delete all NatWest cookies from your browser and hey presto it works again - only irritation is that it loses your saved Customer Number - so make sure you know this before clearing the cookies.
Mrs sqad also has has problems with Nat West online.
I keeps asking her at one stage for her credit card details and tells her just to continue if one doesn't have a debit card.When one continues, one gets to a darkened page, which is impossible to move.
Try clearing all the NatWest cookies, sqad - or (possibly easier) start a private browsing session so that no cookies are stored or used during the banking process.