SCCM ConfigMgr 2012 R2 SP1 Error creating CTM job (0x80070003)

Issue:  After upgrading Configmgr 2012 R2 CU4 clients to ConfigMgr 2012 R2 SP1 clients, some, but not all, clients started having issues downloading content.  It seemed to only happen on clients which just so happened to be our Management Points, or our Software Update Points, so likely this particular error won't be seen much.  But in looking for the keywords of "error creating CTM job", where the error code was 0x80070003, there wasn't anything I could find via any popular search engine. 

Symptoms:  In those clients' local ContentTransferManager.log if you didn't have debuglogging enabled, it was simply this error, repeated every time a download request was attempted:

Error creating CTM job (0x80070003)

If one turned on debuglogging, you got a little bit more information, but not much:

In CContentTransferManager::DownloadContentEx7 Directory::Exists(szDestPath), HRESULT=80070003 (e:\nts_sccm_release\sms\framework\ccmctm\ctmanager.cpp,390) Error creating CTM job (0x80070003)

In those clients' local CAS.log, you'd see this error:

CcmContentTransferManager:DownloadContent failed with error 0x80070003

Diagnosis:  80070003, that error, is supposed to mean something like "the system cannot find the path specified".  We wondered if it was because many of these clients happened to be Management Points, so their installed location for the CM Client wasn't %windir%\ccm, but was <drive letter>:\SMS_CCM.  But that didn't make sense, only some of them were like that, others were in %windir%\ccm.  What it ended up being was a confused (or corrupt) ccmcache folder.

Fix:  Since this is about downloading into cache, and 8007003 is supposed to mean "can't find the path", we moved the location of ccmcache, temporarily (using the Control Panel applet).  What is "supposed" to happen is that when you do that, the former location should be automatically deleted.  That did NOT happen--so clearly something was messed up with it.  Deleted the old location manually, and then put the cache location RIGHT BACK to the normal cache location.  And then content can download.