Linux can't see my files while Windows can.

Does the folder begin with a "."? If so, this is the notation for hidden files under unix systems. To view them you will need to select view->show hidden files.

Nope, the folder is named as normal, with no "." at the beginning or anything. I can still go into the folder, but the files located within are not there. At least, not visible or in any way accessable.

For further information, when I right-click and go into the properties for the folder, I see that under "group" folder access is listed as "none". I don't know if this is in anyway related to my problem, but I noticed that if I try to fix this by changing the folder/file access to let me access files and such, whenever I click "apply permissions" it resets to "none".

NTFS and win32 do not support unix permissions, this is why the group is set to "none".

You might not have read access to the folder if you can see the folder itself, and then not see the contents. I thought originally you could not see the folder.

Can you open a terminal (Ctrl+alt+T, or from applications menu) and then enter this command and paste the result here?

mount

Here's what I get when entering the "mount" command:

/dev/sdal on / type ext3 (rw,realatime,errors=remount-ro)
proc on /proc type proc (rw)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type tmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/paul/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=paul)
/dev/sbdl on /media/Expansion Drive type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096)

There ya go. I should add that I can access other folders on the external in Ubuntu, it's just this one folder that's giving me fits.

Did you type out the above? You can copy and paste it to save time :)

Nothing is jumping out at me as explicitly wrong here (aside from my comment below).
can you run the file-manager as administrator (root) and then see if this lets you find the files?

run the following command:
gksudo nautilus

Something is wrong with your /dev/sda1 (errors=remount-ro); which is running your ubuntu partition, by the way (errors=remount-ro).

You should run a liveCD and fsck it with the fsck command

sudo fsck NAME_OF_FILESYSTEM

the naming might change; currently its /dev/sda1, so the command (if the naming stayed the same) would be

sudo fsck ./dev/sda1

to check the naming -> disk info mapping, you can use

sudo fdisk -l

Even when I run the file manager using the root, the files are missing yet the folder itself is there (gksudo nautilus).

When you mentioned running a liveCD, do you mean fsck-ing with a physical CD of Ubuntu in the drive, or something else? Because I don't have access to a physical CD of Ubuntu at this time.

Also, when I go sudo fsck, I get "fsck.ext3 [-panyrcdfvDFV] [-b superblock] etc. All of the -whatever. What should I do with the fsck?

I need firstly type of file system of external drive. Could be FAT32 or NTFS.
Please run command provided by mycae:
   sudo fdisk -l
where "-l" is lower case "-L" @mycae: please add this data else people will type "one" or "pipe"

"liveCD": it's Ubuntu CD/USB stick on which you boot, but you select "Try without install" instead of "Installation". You will get a Linux Live Session, with system files on CD.

You did fsck on wrong device, as ext3 is a Linux file system types, and I will be very surprised you bought a disk with such system.
Don't bother for the moment about fsck, I presume your disk was not correctly detected by Ubuntu and not mounted.

You can have a look at:
   https://help.ubuntu.com/community/AutomaticallyMountPartitions
   https://help.ubuntu.com/community/Mount
   https://help.ubuntu.com/community/Mount/USB
   https://help.ubuntu.com/community/MountingWindowsPartitions