Do a clean install; that helped with my c250.
A clean install, by my definition, involves backing up your .rockbox directory as it is now, then deleting it from your DAP (or at least rename it to something else). Then, "install" the latest build (I used one from Feb. 15) as you normally would. This way, you have a fresh setup of Rockbox.
Boot into Rockbox at least once and reconfigure anything you need to (set up theme, backlight, etc.), and reinitialize your database. Then, manually copy any extra themes, etc. from your old .rockbox folder, or reinstall them the "normal" way.
It doesn't take that long, and you can always restore your old .rockbox folder if it doesn't work out right.
Not that you won't ever see that delay again, but it should be rare.