Phone call makes Router Crash

Hi,

Lately I've been having a problem with my Internet and Phone Calls.
Each time one specified person calls Internet falls off and I've to restart the router to make it work again.
When other people call there's no problem at all, everything works fine.
Only when that person calls it happens.

Now my phones are connected with the same modem as my computer do, but there's never been a problem before and we have that connection for over 3 years.

Anyone got an explanation?

P.S: Maybe off-topic but my microwave stated weird numbers and all lights (to show when your dinner's ready) started to flicker.

~Thank You for your help

 

have a dsl filter on each phone in your house including caller id device , fax