I'm pretty sure in NBA Live 05 you have to trade salaries within 20% of eachother, so if your giving up 10mil in salaries, you have to receive 8mil minimum. Best way to clear up cap space is to acquire expiring contracts. Goto GMS Desk/Upcoming Free Agents/Entire League and sort by highest contract. Grab a bunch of expiring deals and hit the free agent market!
Also, if you are resigned to being over the cap and dont want to go into the free agent market, resign your players on negative geared contract (that get 10% less expensive each year) this works great when you have 3 or so core players coming off contract the same year and resigning for 5-7 years each, by the time they are at the end of their deal they're at the top of their game and cheap as, so you can sign some role players in FA's and get that championship