(7.14) Uncaught exception thrown in shutdown function... includes/lock.inc

Linux, PHP version 5.2.17, MySQL version 5.0.92-50
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btw - I was unsure about the 'Component' to select so I selected 'base system'.
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Hello.

Out of the blue, on a development site that I had not visited for a couple of days, when I came back to it, I saw the following error message and an inability to access the site:

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Error
The website encountered an unexpected error. Please try again later.
Error message
PDOException: SQLSTATE[HY000]: General error: 1033 Incorrect information in file: './account_drupal/prefix_semaphore.frm': SELECT expire, value FROM {semaphore} WHERE name = :name; Array ( [:name] => variable_init ) in lock_may_be_available() (line 167 of /home/foodir/public_html/foo/includes/lock.inc).
Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[HY000]: General error: 1033 Incorrect information in file: './account_drupal/prefix_semaphore.frm': DELETE FROM {semaphore} WHERE (value = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] => 237664863502619e5a6abe4.73303112 ) in lock_release_all() (line 269 of /home/foodir/public_html/foo/includes/lock.inc).
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Q: What might be the cause for this registry issue?
It affected 3 different installed D7 flavors (3 folders) in the one hosting account.

Q: How often might this reoccur?

Q: How to prevent it from reoccurring?

Q: Is this a bug in the software?

I did find a solution that worked -- rebuild registry per http://drupal.org/node/1565138 (#9) => http://drupal.org/project/registry_rebuild
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Thanks.