Terastation TS-RVHL RAID6, 2 drives failed.... not sure if it is rebuilding.

[smace@chathamhospital.org]

I have a Terastation TS-RVHL, 4 3TB drives, set up as RAID 6.

Today, two drives failed (1 and 3).  It instructed me to replace both drives, which I did with Buffalo replacements.

I followed the replacement instructions, and when the red LEDs changed to blinking for both drive 1 and 3, I pressed the function button until it beeped.

Drive 3 is now "green" on the front panel, drive 1 is still blinking red, the display is prompting me to push the function button again, but it does not respond.

If I attempt to log in via the web interface, I get a message:
"Changing RAID Array...
Cannot change all of the configurations until changing Raid Array is completed. Also share folder service is not working.
Details
Progress: 10 %"

It has been here for over an hour. Before I replaced the drives, I could access the shares; now I cannot.

Is this expected behavior?  Should I have only replaced one drive at a time?