Isn't that card based on a SysKonnect chip?
I know Solaris supports quite a few SK products, seeing as I've used some myself 🙂
If so, you could probably make it work, but it's a fairly hairy procedure with no guarantees, but I could give you a few pointers if you'd like.
Another way would be to check if OpenSolaris supports said NIC, not exactly the same as "Just Solaris", but close enough if it's for home use or some such.