we receive NaAPIFailedException: Unable to create iterator (errno=13001) exception when we iterate through the cifs shares.
Following the advice in this community (http://communities.netapp.com/thread/6106), we checked the space on the root volume. It has only 2% used (out of 200GB). So this could not be the reason for the exception.
An other discussion thread (http://communities.netapp.com/message/1368) is fairly old where it was communicated that there is a bug in ONTAP when parallel calls happen (just the same msec). But we also receive the error sporadicly, when only one request was sent to ONTAP.
I know this thread is a bit old,yet I'd like to share a possible solution:
connect to your filer c$\etc and look for a folder called .zapi - this folder is most likely full! Rename it to e.g. .zapi_ and then restart your web api session again. It will be recreated and you can work again!