Connection problems since new protection

I've recently switched from AVG to Kaspersky Internet Security 2013. My laptop and my daughter's (both running Windows 7) are fine but my wife's (running Windows XP) keeps losing its internet connection (O2). It drops out and back in with annoying frequency sometimes, usually in the evenings.

Is anyone aware of any issues with Kaspersky or please can anyone suggest a possible cause?

Thanks.