The 2950 is a layer 2 switch only which means yu can only have one L3 vlan interface up at any one time. So you can have multiple L2 vlans on the switch but only 1 "interface vlan x" up.
The L3 vlan interface on a Layer 2 switch is purely used to manage the switch and not for routing between vlans. If you want to be able to have multiple vlan interfaces up at the same time you need a L3 switch eg. 3560/3750/4500/6500.
HTH
Jon