A few people have reported Speedtouch DSL modem problems under Tiger that did not exist before under Panther. The solution they found was to get an ethernet router to route the connection to their computer. An Apple Airport or 802.11b/802.11g router can also serve the same function. The problem appears to be in those DSL modems not having the proper drivers installed. Not all ethernet DSL modems require specialized manufacturer drivers for installation. I've used several Speedtouch modems on prior DSL services that did not require any specialized drivers. Contact Speedtouch if you find your modem appears to be one that does:
If your modem is a USB DSL modem by Speedtouch, find out from Speedtouch if you can use ethernet instead of USB. Many have found this to be more reliable.