Problems importing D7 into WAMPserver

Hi,
I've been with Drupal for 5 or 6 years - working on an XP laptop and an old WAMP instalation, and never had such a problem. Now I've finally built a powerful desktop with Windows7 and WAMPserver. I've exported all of my old 43 databases and imported them into the new WAMPserver. The results are unpredictable at best:
the Drupal 5 projects work like a charm (D5 is as simple and reliable as an AK-47)
the Drupal6 projects work on and off (I'm assuming that admin_menu module is causing some hickups, but it'simpossible to get to /admin section at all)
BUT Drupal7 projects are not working at all ! In most cases of D7 I get this:

Error
The website encountered an unexpected error. Please try again later.
PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'drup7.semaphore' doesn't exist: SELECT expire, value FROM {semaphore} WHERE name = :name; Array ( [:name] => variable_init ) in lock_may_be_available() (line 167 of C:\wamp\www\drup7\includes\lock.inc).
Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'drup7.semaphore' doesn't exist: DELETE FROM {semaphore} WHERE (value = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] => 158732020650e8f36d253303.83017425 ) in lock_release_all() (line 269 of C:\wamp\www\drup7\includes\lock.inc).

Can someone please advise what's going on? and how to correct this?