I'm running the 32-bit version of Eclipse, and now that I upgraded to the 64-bit java sdk, eclipse won't run anymore.
Why is this the case, and how can I fix it?
Eclipse won't run because Eclipse ships with a native launcher (an executable) which loads and runs the underlying Java runtime. By doing this, the java architecture must match the executable architecture which loads it. The same will be true if your Java code loads any shared native libraries.
Your solution: Get 64bit Eclipse