BUT... can someone explain to me why my landlord's PC wasn't affected in the same way?
Some modems are trained to ignore the fact the dial tone is not constant - I've noticed that in computers I've installed over the last two years or so -i.e. about the time when vmail invaded the UK.
You can set your modem to ignore the dial tone - somewhere in the settings, that way it won't listen out for it and just dial regardless, then you will never have to bothe...ahem ask for our assistance again
Reminds me of a warranty job I did for a Japanese customer 2-3 years ago; I was sent out with two spare modems to fix to identical brand-new computers which he was trying to set up to the net, both unsuccesfully. As I arrived my first instinct was to pick up a telephone receiver to check the line was ok (working your way backwards to the problem technique..!).
Anyway as he was talking I switched off the dial tone detect and connected to the net no problem. At that point he told me that he had been on the phone to the manufacturer for hours, then Microsoft and finally BT. He was really stressed out about it and I come along and fix in 90 seconds! I literally left him with tears rolling down his cheek. Of course I gave him a good slap and told him to pull himself together, not. Actually I felt a bit sorry for him 'cause if you're on a call desk it's kinda one of the things you should have checked to make sure the modem is actually capable of dialling - if it doesn't the modem's broken, if it does the cable/phone line are possible suspects. Simple.
Anyway, that's my words quota for the day.
Cheerio
amofw