Converting Polys to SubDivs Problem
 

I'm reletivly new to Maya and I've been having a problem converting Polygons to Sub-Divs. I downloaded the Cartoon Dog tutorial and followed it as best I could. I had some trouble using booleans: Union so I used the longer method in combining everything. After that I tried to convert the polys into sub-divs then this message appeared in the script editor:

// Error: polyToSubdiv1 (Poly To Subdiv Node): One or more edges is nonmanifold.
// Nonmanifold geometry cannot be converted to a subdivision surface.
// To clean up nonmanifold edges, use Polygons->Cleanup with the nonmanifold option. //

First of all I don't even know what a Nonmanifold is. But I did what it said and I went to Polygons-> Cleanup with the nonmanifold option on. Then after I did that I could change it into Sub-Divs but my model was messed up. Sections where missing and circles were in some sections surrounded by nothing. My model was cut up.

Can anyone help me out?

on the leg, the vertices arn't merged.