The sync error is not created by Pocket Informant, but received from the server you are syncing with. In most cases these errors occur when the server is overloaded, exhibiting networking issues, or you are seeing network problems due to proxies and/or network monitoring software.

Steps to fix most sync errors include:

• Trying to sync on a different network. Some networks, such as Orange, use proxy servers to save bandwidth and sometimes these will mess up the network data and cause sync errors.
• Reset Sync. Some servers, such as Google, sometimes have trouble with some calendars when being passed date based queries as we must for sync to properly occur. This usually happens when a calendar on the server presents the server with a problem. For example in early 2010 "Remember the Milk" calendars would cause problems on the Google servers when Pocket Informant (or any Google API app) would query them. Reset Sync does a full non-query pull of the server data.
• Try again later. Especially when software upgrades are made, such as Pocket Informant, Google's Calendar API servers become overloaded with tens, if not hundreds of thousands of users doing sync queries at any one time. Since Calendar API servers are not as plentiful as their search counterparts, they become busy and can fail.

The raw error message is:

We understand how frustrating sync issues can be and realize that when sync troubles occur you just want it fixed and prefer not to deal with the blame of why its happening; however to be able to best solve the issue we must find the cause. If its our bug we can fix it after we reproduce it. If its a service issue with Google or Toodledo or any other sync partner, then we need to identify that so we can engineer a workaround or work with the partner on their issue to solve it for you.