I've been getting errors like General error: Can't create/write to file , Error 2006: MySQL server has gone away , and other similar PDOExceptions and errors from time to time while developing on my Mac using MAMP Pro (this seems to happen more often with Drupal 7 sites than Drupal 6, for reasons I know not). I've noticed a few other developers are getting these errors too, and almost always on local environments as opposed to live servers.

I found that the easiest way to deal with them is by giving MySQL a nice buffer of memory via the max_allowed_packet and innodb_buffer_pool_size settings. Just bump those up to 256M or higher, and the errors above should go away. (In MAMP Pro, just go to File > Edit Templates > my.cnf, and search for those variables. Uncomment the innodb_buffer_pool_size variable if it's commented out.

Typically this only happens if you're working with rather large databases, or if you're doing things like clearing all caches with a low max_allowed_packet size. Some people drop the entire database and reimport, but that seems like overkill to me—especially since I can always throw more RAM at a problem!

Further reading: MySQL has gone away [MySQL Reference Manual]