Having troubles reading usb external drives.

Question

I have a macbook pro, mid 2010 is when I got it.  The issue I've ran into for about 6 months now is my usb external drives are not currently being recognized.  It's only external drives and thumb drives though.  My mac recognizes my iphone, charges my camera usb, lets me use a usb midi controller.  About six months ago I was having trouble connecting a usb dmx lighting interface.  I called the company and they sent me to a workaround and it worked.  http://groups.google.com/group/dmxis_users/browse_thread/thread/c5746c10c618bf19 ?hl=en_US 
Ever since then, it's never been the same my external drives don't work.  I even took it to an apple store and replaced the internal boards.  (Sorry for not knowing specifics)  Any suggestions or ideas would be greatly appreciated!

Answer 1

That would explain your problem!  If you have a backup then see if it's on your backup.  Otherwise, you will need to restore it from your installer DVD using Pacifist:
How Restore Deleted or Missing OS X Components
A few of the basic OS X installed applications can be restored from the Optional Installs installer located in the Optional installs folder on your Installer DVD.  However, if what you need is not there then follow the instructions below.
How to Use Pacifist to Restore Deleted or Missing OS X Components
Insert the OS X Installer DVD into the optical drive.  Use a simple utility like TinkerTool to toggle invisibility so you can see invisible items.  Alternatively, open the Terminal application in your Utilities folder and at the prompt enter the following:
defaults write com.apple.finder AppleShowAllFiles Yes Press RETURN.
To turn off the display of invisible files repeat the above command substituting No for Yes.
The install packages are located in the /System/Installation/ folder on the DVD.
Download the shareware utility Pacifist from VersionTracker or MacUpdate. Use it to extract a fresh copy of the missing item(s) from the file archives on your OS X installation DVD. The file archives are in the /System/Installations/ folder (use Go to Folder option in the Go menu of the Finder.)
Here are Four Basic ways to use Pacifist (courtesy of George Orville.)
A. Drag a .pkg icon onto the Pacifist window .....proceed to step 7.
B. Click on “Open Package ....” and navigate to package desired and click “Open” in the open/save window.....proceed to step 7.
C. Insert Mac OS X installer CD and when it mounts, navigate to .... Menu->Go->Go to Folder. In the path field enter or paste ....
/Volumes/disc name/System/Installation/Packages (where disc name is the name of the CD/DVD that you inserted.
• Click on the  "Go" button ..... • Drag a .pkg to Pacifist..... proceed to step 7.
The package you'll need will have to be discovered by trial and error, but for most applications you should start with the Essentials.pkg and/or Additional Essentials.pkg.
D. Insert your Mac OS X install disk 1 .... and open Pacifist.
1. In Pacifist, select "Open Mac OS X Install Packages" ... dialog may appear asking for disk 2, then disk 3 and finally disk 1 again.... {if DVD is not used)...If “Stop Loading” is selected...the procedure will stop!!!
2a. When loading is complete, a new window appears, click the triangle to display contents of each package...Select item and proceed to step 7.
2b. or click the “Find” icon in the Pacifist window and type the name of the software you need.
3. In the list that comes back, click the top most entry for the item that you want. ..... that is the one for the English language.
4. On the top of the Pacifist window, click “verify” .... you will probably be prompted for your password.
>5. Enter checks for.... “verify permissions” and “verify file contents.” and click “verify” ....enter password when prompted.... you will get back output which may look like this:
20 files were scanned. 20 of 20 files were present on the hard disk. 0 of 20 files had file permissions that did not match those specified in the package. 0 of 20 files had checksums that did not match those specified in the package.
6. Click “close”. Go to step 7.
Extract or Install........
7. In the Toolbar (upper left), you now have the option to extract or install. Click a file in the lower list and those two icons will be enabled.
8. If “Extract to...” is selected.... navigate to the location where the file will be placed, select “choose”, select “extract” in new dialog that appears,authenicate , if prompted, click “OK”.
9. In the next dialog, click “Extract”.
10. If “Install” is selected... dialog will appear with the location/path of the installed software. Click “Install”
11. Type in your password, click “OK”
Pacifist will begin to extract files.
12. In steps 8/10ß.... you also have the choice to “cancel”
Notes.....
Pacifist may find that a file it is installing already exists on the hard disk. Pacifist will present you with an alert panel....
Stop Leave original alone Update ..... Default selection Replace .... Replace option should only be used on full install packages