Problem---->

Nonmanifold geometry cannot be converted to a subdivision surface.
// To clean up nonmanifold vertices, use Polygons->Cleanup with the nonmanifold option. //
// Error: Command polyToSubdiv failed. Open Script Editor for details. //

this error comes up when i try convert polys to sub divs, i know its to do with one of the corners of a cycliner which i closed up (wth resize tool) so it came to a point. When i use the Nonmanifold cleanup option it allows me to convert into sub divs but the area were i close these vertices up looks like a bunch of petals and they are all seperate and crap.

I tried going to the area and selecting vertices and merging them all together but this then said i have to do a Nonmanifold cleaup, and when i do the cleanup it converts back into seperate faces.

Can somone pls explain whats goin on?

Also i have been watching the tutorials and he says to try keep like vertices with only 4 sizes or something, why is this? The vertice that keeps on giving this Nonmanifold error has about 20 lines connecting to it before i do the cleaup but after they all disjoint from it and i get about 30 more vertices.

Anyways thx
josh