if i understood right you softmodded your wii, following the (excellent) guide of xzxero ( http://gbatemp.net/index.php?showtopic=171901 ). Since i expierienced the same thing myself a few days ago softmodding a virgin wii 4.2E few days ago, i can easily help you by reccommending you to enter the priiloader (former preloader) by booting up your wii and keeping pressed the reset button.Once you get in the priiloader menu you should go to system hacks menu and enable the option which blocks the disk update.save and exit.that's all. if i understood the situation you are in. good luck.

 

about the freezing problem.
i would check out the disk, meaning the spindown problem which some disk face and as a result provoce the sintoms you encounter.
to solve this, you should attach the hard disk to your pc , download the disc utilities from the manufacturer , access the disk through the utility and disable the spindown option.
P.S. the time lag you wrote about (30 seconds to 1 minute) is pretty short to incriminate the spindown issue , but if i was you i would give it a try.
P.S.2. since you are using usbloader gx (with a high revision number), you could create a folder in the root named wbfs in another external disk transfering in this folder a couple of games through WiiBackupManager0.3.3 in wbfs file format and check out if the problem is persisting.
usb loader gx can boot games from a fat32 or ntfs formatted disk now, so you can avoid formatting in wbfs and lose precious data.this was told just to check out if the problem is the disk you are actually using now.

 

I perfer to use wiiflow or configurable usb loader....maybe you should try one of them, they work perfect for me. see if you get the same problem