My Linux Mint doesn't support my USB flash drive properly

This could be an /etc/fstab issue.

Run dmesg after plugging the device. You will get something like the following:

sd 7:0:0:0: [sdc] 8028160 512-byte logical blocks: (4.11 GB/3.82 GiB)
sd 7:0:0:0: [sdc] Write Protect is off
sd 7:0:0:0: [sdc] Mode Sense: 03 00 00 00
sd 7:0:0:0: [sdc] Assuming drive cache: write through
sd 7:0:0:0: [sdc] Assuming drive cache: write through
 sdc:
sd 7:0:0:0: [sdc] Assuming drive cache: write through
sd 7:0:0:0: [sdc] Attached SCSI removable disk

The value in the brackets is the device. For the answer's purposes, I will use sdc. Yours may be different.

Go to the /mnt directory and run mkdir usb

Then, run su -c "nano /etc/fstab" and add a line like this:

/dev/sdc    /mnt/usb  auto user 0 0

Save.

Reboot and you should be able to find the device in your file manager and mount it as any user, with read-write access under the directory /mnt/usb.

This is my solution for a distro without an automounter (Zenwalk). You may have a problem with your automounter, and that is a different can of worms.

Also, kernel version (ie uname -r) and file manager may affect this.

The problem was related to the automounter in my case. I was using ndiswrapper for wifi communication through usb the other day and it seems it disabled the usb automount.

To fix it you need to do this:

sudo gedit /etc/modules

And you need to add the following lines:

usb_storage
usbhid

Source: Web Upd8: Ubuntu / Linux blog - Fix USB devices' automount not working.