Anti-virus company Symantec is reeling from a series of mishaps this week that may have cost it dear in customer numbers.

Yesterday, the company issued a patch for its LiveUpdate feature that could have allowed someone with network access to bypass security into privileged areas. The problem affected all except the most recent version (2.0) of its Norton Anti-Virus suite and stemmed from the LiveUpdate Help wrongly being given system privileges.

Symantec has sought to play down the issue - pointing out that it only refers to retail version. Only if the user can get access to LiveUpdate and only if a certain configuration is in place can the exploit be used - but any problem at all with automated update features in software gives people the fear.

No one likes allowing a company direct access to your computer and so there is a huge element of trust involved. Especially since LiveUpdate is used to protect against viruses and the like. It is therefore bound to be the Holy Grail for virus writers. If you trade on this trust, even a small question mark is enough to shake things up.

But this relatively minor security issue was made all the larger because of a problem earlier in the week. Users of Symantec's software suddenly found their computers were seizing up and fundamental programs such as Word and Excel would not start.

It wasn't Symantec's fault. It uses VeriSign digital certificates to check its software hasn't been tampered with (or pirated) but VeriSign had that day decided to end various other certificates and so its servers were swamped with millions of requests for new ones. The server couldn't cope but Norton Anti-Virus wouldn't budge until it had confirmation.

Symantec fairly swiftly explained how to bypass the problem but to many people's minds Norton software was causing the problem and more than a few made it clear they would switch to a competing anti-virus software vendor rather than cough up Symantec's £25-a-year service fee.

What will make Symantec executives really sick though is that at the same time as its image has been tarnished, a far more serious security issue concerning its competitors McAfee, Trendmicro and Kaspersky in which a small malicious file can be used to knock over a system because of a mistake in their scanning technology, has gone past barely unnoticed.