One last step to be certain, update-grub , then reboot! 
it gave me this, is it a problem?
[manjaro /]# update-grub
Generating grub configuration file …
Found theme: /usr/share/grub/themes/manjaro/theme.txt
Found linux image: /boot/vmlinuz-5.7-x86_64
Found initrd image: /boot/intel-ucode.img /boot/initramfs-5.7-x86_64.img
Found initrd fallback image: /boot/initramfs-5.7-x86_64-fallback.img
Found linux image: /boot/vmlinuz-5.4-x86_64
Found initrd image: /boot/intel-ucode.img /boot/initramfs-5.4-x86_64.img
Found initrd fallback image: /boot/initramfs-5.4-x86_64-fallback.img
grub-probe: error: cannot find a GRUB drive for /dev/sdb1. Check your device.map.
grub-probe: error: cannot find a GRUB drive for /dev/sdb1. Check your device.map.
Found memtest86+ image: /boot/memtest86+/memtest.bin
done
Oh, that is fine! 
That’s GRUB trying to probe your live USB …
You may reboot successfully, now!
It worked! Thank you very much!
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Sweet!!
Glad it worked !! Thank you for your patience!!
2 Likes
Sure, this is a Manjaro support forum after all. ISOs aren’t that hard to get (Manjaro - Downloads) and perhaps there is even a bootable usb left over from initial installation.
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You’re a genius! I had a similar issue and it worked perfectly. You saved my life bro
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Hello @The_Quantum_Alpha. I am experiencing the failure to load kernel modules error on boot as well. I also found this post but as I am not an expert with linux, I am struggling to interpret the suggested solution.
I tried your recommend solution, but on pacman -R linux54 it errors with:
checking dependencies…
:: removing linux54 breaks dependency ‘linux54’ required by linux54-nvida-340xx
:: removing linux54 breaks dependency ‘linux54’ required by linux54-virtualbox-host-modules
It was suggested to me to use mhwd-kernel -r linux54 instead. With that in mind, would the following be the correct command to resolve the load kernel modules error?
sudo pacman -S linux510 && mkinitcpio -P && mhwd-kernel -r linux54 && mkinitcpio -P && pacman -S linux54 && mkinitcpio -P && pacman -R linux510 && mkinitcpio -P
Thanks!
You can indeed give it a shot!
If not, let me know!
@The_Quantum_Alpha, I gave it a shot.
Error: You can’t remove your current kernel.
Let’s see 
Try the following command : sudo pacman -S linux510 && mkinitcpio -P && pacman -Rdd linux 54 linux54-nvidia-340xx linux54-virtualbox-host-modules && mkinitcpio -P && pacman -S linux54 && mkinitcpio -P && pacman -R linux510 && mkinitcpio -P
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This time I got the following two errors:
error: target not found: linux
error: target not found: 54
Should the command be changed to sudo pacman -S linux510 && mkinitcpio -P && pacman -Rdd linux54 linux54-nvidia-340xx linux54-virtualbox-host-modules && mkinitcpio -P && pacman -S linux54 && mkinitcpio -P && pacman -R linux510 && mkinitcpio -P?
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Oups! My bad, sorry!
Indeed, remove that space!
That command finished. I will run update-grub and then reboot. Hopefully the kernel is able to load on reboot.
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The screen is black after reboot. I am able to select Manjaro Linux on boot screen, but just get black screen. I can still access TTY2.
is your GPU AMD, may I ask?
Hi @The_Quantum_Alpha, I hope this answers your GPU question
lspci
01:00.0 VGA compatible controller: NVIDIA Corporation G98M [Quadro NVS 160M] (rev a1)
I ran sudo mhwd -a pci nonfree 0300 to try to install drivers, but it returned Skipping already installed config 'video-linux' for device: 0000:01:00.0 (0300:10de:06eb) Display controller nVidia Corporation G98M [Quadro NVS 160M].
However, the driver doesn’t appear to be recognized:
inxi -G
Graphics: Device-1: NVIDIA G98M [Quadro NVS 160M] driver: N/A
Try pressing ctl+alt+F2 to get to a tty. Then type sudo modprobe nouveau. See if you get a GUI that way.
I will tell you I switched to Nouveau and am completely satisfied.
1 Like
Thanks @deroberts1. I was able to get the gui issue eventually resolved thanks to the friendly people on this forum. Solution for me was to remove nvidia drivers and use only the opensource drivers. Thanks!
Good for you. I believe open source is the way forward with the ongoing work on Wayland beginning to bear fruit.