Invalid Variable

I'm getting the the following error with the latest dev version when importing (similiar to this thread, but I have no errors in my CSV--imports will complete--but the error persists throughout the upload process)

Notice: unserialize() [function.unserialize]: Error at offset 0 of 32 bytes in /opt/lampp/htdocs/mysite/includes/bootstrap.inc on line 559

Debugged with the variable module (see attached) and found an invalid entry:

Name Value
node_import:lock 5335c4c9d934ccdd559261725d074b1b