It sounds like you are trying to use the CU500 as "Phone as a Modem" for your internet connection - I have done with successfully with a RAZR, but have not yet gotten it to work with the CU500 (on either my PC or my MacBook). What software, if any, are you using on the Mac with your CU500? I have been sticking to BitPim (and recommend it). I am given to understand that OSX 10.4.9, the next update to Tiger should fully support the CU500, so that might be something to hang in there for (depending on what version of the operating system you have now).