I had a similar situation w/ my old LG phone when I upgraded to Windows 7 64 bit. I think it is an issue that the phone manufacturers haven't worked out with Microsoft yet, despite the fact that Windows 7 has been around over 1 year. No excuse for it, but I feel your pain. I resolved the issue by getting an Android phone instead.
BTW: My computer was previously running Vista but I had to do a complete re-install to upgrade to Windows 7. Don't think it has to do with your computer's previous configuration.
I have a Samsung Vibrant phone from T-mobile that is no longer being recognized by my computer. I have a Lenovo u450p laptop running Windows 7 Home Premium 64 bit. Even when it used to be recognized by my computer, it was intermittently working. Now my phone is not recognized at all when I connect it via USB.
The drivers on Samsung's website do not work after installation, so I wonder if there might be issues relating to my computer's past driver files and installations.
If anyone has had similar issues, please let me know what you have done to correct them. I have tried searching google for this problem and most of the alternative fixes haven't worked for me. Any help would be appreciated. Thanks.