Call of Duty: Black Ops patch v1.09 has been rolled out to Steam users today, fixing numerous issues in Multiplayer and Zombie Mode. Some fixes include improved memory utilization for multiplayer matches, better DLC filter for the server browser, and fine-tuning damage received from napalm and bombing runs when you're inside a building. The full list of changes can be found in the source link below.
This patch also prepares Black Ops to support the upcoming mod tools release. Treyarch intends to have the tools out by the end of May but have still yet to detail what can be done with the tools.
Update: Treyarch is delaying the release of the mod tools due to some unspecified issues that popped up. A new release date was not given but Treyarch did confirm mods will only run on unranked servers.