I think that you've got Japanese stilt grass there. It's an annual that makes a jillion seeds a year; if you can pull it up before it seeds, you'll have MUCH less to deal with next year. I know it's a royal pain, but it's really the only way that works, especially if it has gotten among plants that you want. The good thing is that it comes right up. If you're not sure that it's stiltgrass, post a closer picture here or on the Name That Plant forum.

Here is a link that might be useful: page on stiltgrass