Sometimes the problem isn't with the site, it's with the anti-virus software. The anti-virus companies keep running lists of adware, malware, spam, viruses, etc., and sometimes the information isn't correct or updated. I had this problem a couple of years ago, a company my employer (a law firm) was doing business with was using some kind of software that not only blocked the law firm's emails, it reported our IP address as malware to all the other anti-virus companies, which in turn blocked all our other e-traffic. It was an absolute nightmare to untangle.
I suspect, since some members are not having problems, that the issue isn't with the site, it's with either the anti-virus software or the browser.