If you are encountering a white screen on the Arb page, but all other functions are normal, try this fix:
Close the qt-client and wait a few seconds.
Open the folder C:\Users\
Double click on the one that is your username
Your path now should be something like,
C:\Users\Henry
so then go to
C:\Users\USERNAME\AppData\Roaming\Botcoin
and you should see a file named version.txt
Delete that file, and re-run the qt-client. Let us know if arbitrage is still not working after it re-loads.
Walter