I just got the Map

Question

I just got the Map Update 2008 City Navigator North America NT and did an install of the US on my Garmin 530c. I realized that it did not include Canada cause the 530 does not have enough internal memory. I installed Canada after that cause of an up coming trip. I decided to get a 4 gig SD card and load the US back on the 530 and install Canada on the SD card. When I went to install the US on the 530 it errors out at 69% and says it does not have enough memory. Called Garmin and went through deleting a file but it still fails. It seems that there is stuff stuck in memory that needs to be removed to allow the US to be installed. Any ideas?