Mentioned in [12336] on Core SVN:
Use stripslashes_deep to strip meta values.

Created ticket #10656 on Core Trac:
Creating or updating serialized custom field values via XML-RPC serializes ...

Created ticket #10619 on Core Trac:
Importing WXR breaks serialized postmeta value

Reopened ticket #4028 on Core Trac:
Importing WXR breaks serialized postmeta value

Mentioned in [7884] on Core SVN:
Fix _deprecated_function() and _deprecated_file() so that they work correctly.