Hi, I'm having a similar problem, and when you mention "patching" the boot loader and "flashing" it, I think I'm missing a step. I've downloaded and unzipped the .rockbox folder and rockbox.iaudio file, and those have been copied to the drive (in my case f:\). I then copied x5_fw to the firmware folder on the player.
You must patch x5_fw.bin with the bootloader. Get a copy of mkboot (there is a windows .exe linked in the iaudiophile "noob" tutorial thread) and a copy of the bootloader (called something like "bootloader.bin"; the official bootloader can be found on the rockbox wiki or the dual bootloader can be found in the same iaudiophile thread).
Run mkboot per the instructions ("mkboot -iax5 x5_fw.bin bootloader.bin new_x5_fw.bin"). Copy the resulting x5_fw.bin to the FIRMWARE directory of your X5 (rename it to x5_fw.bin if necessary). Unplug the USB cable, wait 30 seconds and then without turning the player on, plug in the AC adapter. After a second or two the device will display an "Upgrading firmware" message. Leave the device alone until it finishes, then unplug the AC adapter and turn the player on.