I noticed a bug in _payment_gateway_list on Alpha 7e and it seems to be fixed in 8, but the fix is done by manipulating the result of the function instead of the function itself.
Problem: using unset on an array with numeric keys does not reindex the array
uc_payment.module line 1111
<?php
unset($gateways[$i]);
?>Fix: using array_splice does reindex the array
<?php
array_splice($gateways,$i,1);
?>The fix in Alpha 8 was placed in uc_payment_process lines 900 - 902 and uses array_keys to overcome the problem. To prevent any other potential problems with the results of _payment_gateway_list, it might be best to fix it there at the root of the problem.
Any thoughts?