Active Sync Client Sync Message, status code 4 - ParseSyncKey - AirSyncPermanentException - exchange-server-2010

Question

I'm currently writing an active sync client and I've successfully managed to do a folder sync. I'm now attempting to sync the "Notes" folder (using the sync command) and it's giving me an error code 4, which Microsoft describes as "Protocol Error" -- I don't see anything wrong in the protocol that I'm sending, here is the sections from my log:
Folder sync RequestBody :
<?xml version="1.0" encoding="utf-8" ?>
<FolderSync xmlns="FolderHierarchy:">
<SyncKey>0</SyncKey>
</FolderSync>
FolderSync ResponseBody:
<?xml version="1.0" encoding="utf-8" ?>
<FolderSync xmlns="FolderHierarchy:">
<Status>1</Status>
<SyncKey>1</SyncKey>
<Changes>
<Count>12</Count>
<Add>
<ServerId>1</ServerId>
<ParentId>0</ParentId>
<DisplayName>Calendar</DisplayName>
<Type>8</Type>
</Add>
<Add>
<ServerId>2</ServerId>
<ParentId>0</ParentId>
<DisplayName>Contacts</DisplayName>
<Type>9</Type>
</Add>
<Add>
<ServerId>3</ServerId>
<ParentId>0</ParentId>
<DisplayName>Deleted Items</DisplayName>
<Type>4</Type>
</Add>
<Add>
<ServerId>4</ServerId>
<ParentId>0</ParentId>
<DisplayName>Drafts</DisplayName>
<Type>3</Type>
</Add>
<Add>
<ServerId>5</ServerId>
<ParentId>0</ParentId>
<DisplayName>Inbox</DisplayName>
<Type>2</Type>
</Add>
<Add>
<ServerId>6</ServerId>
<ParentId>0</ParentId>
<DisplayName>Journal</DisplayName>
<Type>11</Type>
</Add>
<Add>
<ServerId>7</ServerId>
<ParentId>0</ParentId>
<DisplayName>Junk E-Mail</DisplayName>
<Type>12</Type>
</Add>
<Add>
<ServerId>8</ServerId>
<ParentId>0</ParentId>
<DisplayName>Notes</DisplayName>
<Type>10</Type>
</Add>
<Add>
<ServerId>9</ServerId>
<ParentId>0</ParentId>
<DisplayName>Outbox</DisplayName>
<Type>6</Type>
</Add>
<Add>
<ServerId>10</ServerId>
<ParentId>0</ParentId>
<DisplayName>Sent Items</DisplayName>
<Type>5</Type>
</Add>
<Add>
<ServerId>11</ServerId>
<ParentId>0</ParentId>
<DisplayName>Tasks</DisplayName>
<Type>7</Type>
</Add>
<Add>
<ServerId>RI</ServerId>
<ParentId>0</ParentId>
<DisplayName>RecipientInfo</DisplayName>
<Type>19</Type>
</Add>
</Changes>
</FolderSync>
My Sync RequestBody :
<?xml version="1.0" encoding="utf-8" ?>
<Sync xmlns="AirSync:">
<Collections>
<Collection>
<SyncKey>0</SyncKey>
<CollectionId>8</CollectionId>
<DeletesAsMoves>1</DeletesAsMoves>
<GetChanges/>
</Collection>
</Collections>
</Sync>
Lists this exception:
SyncCommand_OnExecute_Exception :
Microsoft.Exchange.AirSync.AirSyncPermanentException
at Microsoft.Exchange.AirSync.SyncCommand.ParseSyncKey(SyncCollection collection)
at Microsoft.Exchange.AirSync.SyncCommand.SyncTheCollection(SyncCollection collection, Boolean createSubscription, Boolean tryNullSync)
at Microsoft.Exchange.AirSync.SyncCommand.OnExecute()
And provides the following ResponseBody :
<?xml version="1.0" encoding="utf-8" ?>
<Sync xmlns="AirSync:">
<Status>4</Status>
</Sync>
Any ideas why it is failing there? This is the first sync of the folder, so the SyncKey SHOULD be 0...

Answer 1

From http://msdn.microsoft.com/en-us/library/gg675447(v=exchg.80).aspx :
A Status element (section 2.2.3.162.16) value of 4 is returned if the GetChanges element is present and empty or set to 1 (TRUE) when the SyncKey element value is 0 (zero). No error is returned if the GetChanges element is absent or set to 0 (FALSE) when the SyncKey value is 0 (zero).
You have present and empty in your xml.
You only may set GetChanges to 1 or live it empty (which is by default = 1) in any consequential sync request, not in initial sync request.