There is speculation that confusion during initial processing of PR applications led to hundreds of applications being deemed incomplete. Guidelines around the validity of Police Certificates are in flux, and it has created logistical barriers for applicants from some countries. Those deemed incomplete were all high scoring individuals, and after having their fees refunded they found themselves back in the pool again. At the next draw in May they were (largely) invited again, raising the required CRS score substantially.
As we have said all along, CIC will have to greatly increase the number of invitations, otherwise they will find themselves unable to meet their annual target for new Permanent Residents. At this point it appears that only the backlog of applications from 2014 will bring CIC close to their targets for 2015. At this point in the year, even with a 6 month promise for processing under Express Entry, there is little chance of many more receiving invitations AND having their applications completed this calendar year.