title: EC2 instance won't connect after changing instance type
body: <p>I changed one Linux instance type from m3.xlarge to r3.xlarge (moar memory).</p>
  
  <p>After starting again the instance I can't connect with SSH, actually it has no ports opened/with running services so it seems that some services haven't started properly, don't know why. However, it responds to ping so system seems to be running.</p>
  
  <p>If I go back to the original instance type it works again. I repeated the process several times and it always is the same, m3.xlarge works fine but r3.xlarge fails.</p>
  
  <p>I know I can create an image and just launch a new instance and (fingers crossed) it will work, but I'm just curious about this issue, why is this happening and how can it be solved.</p>
  
  <p>Any insights? Thanks in advance.</p>