ISS Amateur Radio Project Engineer Kenneth Ransom, N5VHO reports the ARISS digipeater has changed frequency from 145.825 MHz (up/down) to 437.550 MHz (up/down). The same digi alias ARISS is still used.

This change was started with the docking of the ESA Automated Transfer Vehicle (ATV). The ATV is an expendable, unmanned resupply spacecraft delivering propellant, water, air, payloads and experimentalsupplies to the International Space Station (ISS).

Packet operations were moved to the Columbus Module UHF radio when the Kenwood D700 radio was recently powered off due to needing an additional air purifier to support the ATV. Normally the air purifier is located in the ATV but recent power support issues related to the ATV and ISS necessitated the system be relocated to the Service Module. The purifier is now using the power outlet that the 
Kenwood radio normally uses. The Russian team has agreed to briefly power the purifier off for the scheduled ARISS school events but then will re-activate the purifier right afterwards. This appears to be a long term impact as ATV is currently scheduled to depart from ISS in September.

Reference: http://www.hamradionews.net/2012/06/status-of-iss-ham-radio-operations.html