Did you install a 64-bit version of Eclipse like in this thread?
If so, try a 32-bit instead.
The snowleopard.wikidot mentions Eclipse 3.5 being compatible, although:
May require installing Java 1.5 since SL actually only ships with Java 1.6
Regarding your configuration, zvikico adds in the comments:
AFAIK, the Core Duo is a 32 bit processor, not capable of running 64 bit at all.
Even if you install Snow Leopard.
First, you need the 32 bit version. Second, make sure 32 bit Java is your default. You can set it using an application called JavaPreferences, sitting in the /Applications/Utilities.
So:
Here are some installation tutorial (generally for 64-bit version, but can also be usefull for the 32-bit edition)
See Installing Eclipse Galileo on Mac OS X (can be applied to Helios)
Snow Leopard (10.6.x) Users
Download the Mac Cocoa 64-Bit version.
Again, the Carbon version is there in case you encounter compatibility issues with older plugins.
(not anymore with Helios: no Carbon version, only Cocoa)
The main reason you would want to use the 32-Bit version is because of plugins which are incompatible with 64-Bit.
This time, the 32-Bit version will waste your resources because you will cause the OS to start a whole bunch of 32-Bit services.
Read the original post for more details.
See also Java 1.6 & Eclipse on Mac OS X:
Initially, the latest version of Eclipse (3.5) was released only in 32-bit mode for bot:
- Carbon (an older and deprecated Mac OS API) and
- Cocoa (the modern Mac OS API).
Since Leopard only supported Java 1.6 in 64-bit mode, this meant that Eclipse was always running under Java 1.5. With the release of Eclipse 3.5.1, there are now 64-bit Cocoa downloads available, and these will run under Java 1.6.
Everyone apparently agrees that on Snow Leopard you want the 64-bit Cocoa version of Eclipse (unless you are on a 32-bit Intel Mac).