hello, not sure if anyone can help but i hope so.

if u look at the attached file u will see that when i convert to subd the area where there are more than one vertex causes a space. so i did the obvious and merged the vertices that i had accidently created. i also deleted the history by type. and cleanup. but when i then converted again the same happened even though i had merged any extras.
can anyone shed any light on this? i use the option to see how many vertices are selected to help aswell. so they definatly merged before i converted.

thanks