I am running a Mac Pro with osx 10.6.4
and an NVIDA GeForce 7300 GT card. Everything is installed for starcraft 2, but when I load the game up it all works fine untill I go to the character selection screen. It always crashes right after I enter my battle.net account password and it goes to the next screen. I know its under the minimum requirements, but I have run SC2 on old pc laptops I have that are under minimum requirements and it works. I dont care If i lag a bit during battles and such, is there any way to solve this?

No.

hi anthony
i dont think this is a problem with the card.... you card is fine as it manages to get to the character selection screen however its then when everything goes wrong.. which indicates a software based issue and not hardware (i.e graphics card )
in situations like this you should download and install the latest patch(also known as a update) ..however i have just discovered your geforce 7300gt is a unsupported graphics card ( http://starcraft.org/blogs/starcraft/469 ) so this must be were your problem lies
theres a few comments that have been released in regards to running startcraft 2 with nvidia based cards are these are :
"Unless NVidia fixes their bugs, this seems unlikely. At some point, we might make it playable on low settings. This would be in a patch after we ship."
"The NVidia GeForce 7 is not supported because the drivers are too buggy."
"We will optimize the game as much as we can but you should not expect performance parity with Windows anytime soon since it mostly depends on Apple implementing and optimizing the graphic features that we are using."
"Do not use custom graphic settings or the game will have to compile shaders while you play."
note the second comment in regards to geforce 7 series cards... they are not supported because the drivers are seen as too buggy,however this does mean its not a performance or hardware issue, and the good news is that there should be a fix for this online or in the near future
however theres a "Graphics Update for Snow Leopard" which has been seen to fix problems experienced with starcraft 2 when running geforce 7 series cards ( http://osxdaily.com/2010/08/17/download-snow-leopard-graphics-update/ )
i hope this helps,however any problems let me know
good luck anthony !