Find out why your original research adviser dropped you. Make sure that's what happened, actually. "Stopped advising me" can mean a multitude of things. If you're still nominally this person's advisee, either find out how to change advisers and make it so, or find out how to get back on track with your research. Once you've got a clear reason why you've been dropped, figure out how to address whatever shortcomings got you dropped as an advisee. Then, go to your professor's office hours and ask him if he has any openings in his lab group and what you should do in order to become a part of it. Express your interest because he can't read your mind.
The next step is to organize the rest of your academic career in line with the program's scheduling. You should have completed coursework after this many semesters, done reading/testing/whatever by this time, begun work on your diss by this time, and completed it by that time. Sketch out a basic time line with realistic goals to shoot for. Organize your research interests so you know what you have to do before you can start researching, what you should probably need to do while researching. Organize conference opportunities well in advance. Certain ones crop up every year, and you'll know that you have a shot at presenting your personal research, so find out when the submission deadlines usually are (look up last years, for example) and start planning. Organize the work you have already done that is complete or near complete in such a way that you can cobble together an abstract, poster, paper, whatever to submit to a conference. Look through your completed or near complete work and start planning on writing papers to submit for publication.
What to do next? Take charge of your academic career, don't wait for things to happen to you. Sure, your undergrad GPA is going to bite you in some ways. But it's not what's keeping you from getting published, or from presenting, or from working in the labs. It might cause you funding problems, but that means looking for funding more creatively, where your undergrad GPA isn't as much a factor as your letters of recommendation and research proposals. If you aren't a member of your field's professional association(s), join. If you don't know how to organize yourself, find a self-help book or see if your library or school has academic help sessions (many universities do). If you're undermotivated, see the school counselor. Check into organizations like Toastmasters. It's not your adviser's job to lead you; it's your adviser's job to shepherd you, that is, to keep you in the pasture while you're wandering around, doing your own thing.