Yup - just international - I would have a serious look at your line.
Maybee your splitter aint working properly, or, even better, somebody is tapping into your phone line, or, there's a loose-connection type problem on the line.
Plug a phone into the land line (before the splitter and other stuff), and listern to the line quality, press 1, and listern for an echo or a scraping noise...
Do the same after the splitter.
Then check for the flat line when the phone is off the hook - making that drrrr noise.
If the flat line appears when the phone is off the hook, and there is no noise or echo on the other 2 tests, then there must be a problem at the exchange - then - lucky you, you get to call teklom. weeeeeee.
Well - that's my guess, and it's worth a shot (IMHO).