Upgrade your Firefox to the version 2.0 onwards, the latest one. It should work as it may be related with the Firefox v1.5 (somewhere around there) which I assume you are using.

They are good only because the system once belong to Phileo Allied Bank.
Phileo is the first bank to set up an Internet Banking long before all the other banks had come in. I was one of their early users. Pretty advance at that time and it was good. Later, Phileo merged with Maybank during the Bank Negara forced consolidation of banks and the same team move to Maybank. That's why Maybank2u is good until today. Their other services is altogether another matter.