I can't find any reference to it at the moment, but to the best of my knowledge, the visa is still valid. I know this from a friend who's been in exactly this situation (name change after marriage). When you travel, you need to have with you:
- Your old (no longer valid) passport with the (still valid) visa in your old name
- Court document confirming your name change
- Notarised translation of this court document into Russian (this may not be strictly needed, but better have it)
- Your new passport into your new name
If you are still unsure, I suggest you contact Russian Consulate section or a visa agency. If you're in the USA, the phone number of the Russian Consulate visa section in New York is (212) 348-5762. Alternatively the Consulate recommends using an agency called Russian Visa Centre. The phone numbers of that agency are (212) 430-59-90 (in New York) or (202) 827-0880 (in Washington). It won't hurt giving them a call.