Yes it is possible, but you have to use the same crypto map id for both connections, just use different sequence numbers to have the pix see them as seperate connections.
When you have one active vpn connection and want to define and activate the 2nd one, insure that the acl that defines interesting traffic is already defined, and add the crypto map commands that refer to that acl and the remote peer before you config the rest of the ipsec crypto map seq. entries. Otherwise you may find that the pix will block all traffic, including non ipsec, until you have done that. I know that pix 6.1, pix 5.2 and 5.3 code had that issue, it may not be present in the newer code.
