ISP vividwireless had completed a second upgrade of its international link capacity and was investigating another issue that it believed could be impacting broadband speeds on its network.
The issue caused the ISP's chief Martin Mercer to move to reassure customers on its support forums over the weekend.
Mercer said the company was "acutely aware that there have been some issues affecting some customers in recent weeks."
"We moved quickly to provision more backhaul and international link capacity to accommodate customer needs. Capacity was upgraded on 2 August and again on 18 August," he said.
"We have also modified the parameters we use so there should be no repeat of this problem."
He said vividwireless was experiencing "some intermittent difficulties with the efficiency with which network resources operate" and that the issue "can occasionally impact on the speeds customer experience" on the network.
"A specific issue has been identified that is being investigated," Mercer said.
"We expect this to be resolved within a week."
He also denied speculation that the ISP was shaping peer-to-peer downloads on its $75 unlimited plan.
Rather, P2P traffic was being "prioritised below all other traffic... to ensure that all of our customers receive an equally fast internet service", he said.
Mercer advised "heavy" P2P customers to avoid using it between 6pm and 1am.