Get an Ellies Surgetel plug, protects the modem from surges on both telephone line and power and doesnt interfere with the DSL sync.
http://www.ellies.co.za/electrical/FBTWTX
Last season I went through 3 modems in a month, this season touch wood all ok, and my area - Roodekrans attracts lightning strikes. A friend of mine has one and lightning melted the telephone line physically up until the Surgetel, everything else was fine.
They also come with a nice insurance warranty, provided you've sent the warranty card in.