Q: Apps won't update "An error has occurred"

Restart in Safe Mode and see if you can complete the downloads.

http://support.apple.com/kb/HT1564

Are you sure the newest versions of the software are compatible with your OS? You may want to try updating to Mavericks.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the icon grid.

Select

/var/log ▹ appstore.log

from the hierarchical list on the left. If you don't see that list, select

View ▹ Show Log List

from the menu bar. Then select the messages from the last installation or update attempt, starting from the time when you initiated it. If you're not sure when that was, click the Clear Display button in the toolbar of the Console window and then try the installation again.

Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message (command-V).

If there are runs of repeated messages, post only one example of each. Don’t post many repetitions of the same message.

When posting a log extract, be selective. Don't post more than is requested.

Please do not indiscriminately dump thousands of lines from the log into this discussion.

Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.

Please read this whole message before doing anything.
  
This procedure is a diagnostic test. It won’t solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.
   
The purpose of this test is to determine whether the problem is localized to your user account. Enable guest logins* and log in as Guest. Don't use the Safari-only “Guest User” login created by “Find My Mac.”
   
While logged in as Guest, you won’t have access to any of your personal files or settings. Applications will behave as if you were running them for the first time. Don’t be alarmed by this; it’s normal. If you need any passwords or other personal data in order to complete the test, memorize, print, or write them down before you begin.
   
Test while logged in as Guest. Same problem?
     
After testing, log out of the guest account and, in your own account, disable it if you wish. Any files you created in the guest account will be deleted automatically when you log out of it.
  
*Note: If you’ve activated “Find My Mac” or FileVault in OS X 10.7 or later, then you can’t enable the Guest account. The "Guest User" login created by "Find My Mac" is not the same. Create a new account in which to test, and delete it, including its home folder, after testing.

Have you tried to update or install any other apps during this time?

Please post another extract from the log as before, but this time choose All Messages from the query menu.

No. All Messages at the top of the query list. Please do not post all the messages in the log; only the new ones that appear when you try to update in the App Store.

Quit Google Drive and see whether there's an improvement. If not, see below.

In the Console window, look under User Diagnostic Reports for crash reports related to the crashed process (Finder.) The report name starts with the name of the process, and ends with ".crash". Select the most recent report and post the entire contents — again, the text, not a screenshot. In the interest of privacy, I suggest that, before posting, you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header of the report, if it’s present (it may not be.) Please don’t post other kinds of diagnostic report — they're very long and not helpful.