It appears that I am not the only one having this issue which I guess makes me feel better. I purchased my Seido case at Amazon based on previous experiences with their cases and didn't bother checking the reviews and forums first which I now know was a mistake! Oh well it does appear that Seido is aware of the issue and working with those who are having issues to resolve them.
I agree with one of the other posters that there should be clips on the top and bottom of the case rather than on the side as it seems that on the bottom right side the clip always comes out and then the entire case pops off. (From the perspective of holding the phone horizontally with the micro usb on the bottom).
After studying the diagrams and reading all the posts I am sure that I am installing the case properly. Just in case I left a few friends take a stab at putting the case on and they ran into the same issues.
Hopefully a new case will resolve the issue as it has for others and I don't have to worry about the case popping off every time I take it out of my pocket or try and slide the keyboard open!!