Fixed it on my Galaxy s2
I was having the same problem. I would create events on my phone, then after logging into gmail on my computer nothing would show up. I would sync and re sync and nothing was there.
There were two calendars on my phone. My phone calendar and my gmail calendar. I realized this because some events had different colors. On my phone red was gmail synced.... and blue was not, it was phone only. The first thing I did was clicked on all blue events, hit edit, and about half way down there is the option for selecting which calendar you post it to.
To change your default calendar:
Go to calendar - settings - Default Calendar
The very first option says calendar. Select that and you have options for
I selected only the gmail. Now when I create events it only has the option of creating the event on google calendar.
Just to clarify I had to go back and edit previous entries that I had made to change them to google calendar. To do this you have to edit the event, and about half way down you have the option of selecting which calendar it is posted to. I have the feeling if you don't change your previously created events to gmail calendar and you deselect the "my calendar" the will disappear.
Hope this helps!!
I tried not to make it super confusing, but honestly google didn't make this one very intuitive.