This is a known Quickbooks issue and is not anything to do with the LMN Sync tool. After all, LMN is cloud-based and doesn't use disks!
You should be able to hit Try Again (and maybe once for each drive!) and eventually it will work. This is not the easiest fix, but error is coming from Quickbooks, not LMN.
TO TRY TO FIX THE ISSUE:
Make sure you're running the latest update of Quickbooks. See if there are any available updates with your version.
Quickbooks has also released the following support FAQ: http://support.quickbooks.intuit.com/support/articles/SLN63047
Microsoft has also released a suggestion for a fix, in case the issue is in the way your drives were setup: