My guess is what you're suggesting - 60MB would take a while to load, even directly from the SD card. In this case it's going through the virtual image handling, which probably slows it down considerably (and is something that Access could possibly improve), and it also loads from the compressed filesystem of the internal flash. That's usually also slower than an SD card. Certainly much slower than a Class 6 SDHC card.

Have you tried to move the whole .gvm directory to a fast SD card? You could make a symlink from /media/mmc1/.gvm /home/user/.gvm, for example.

(Someone else mentioned a problem with symlinking the gvm store to a card, but I believe I tried the above with success, back with the first beta)