I first heard about this on Adam Spencer's radio programme in the shower this morning (it's so nice to have a geek on my radio). Here's an article about it.
This is all approximately 7km over my head, but E8 is a 248-dimensional Lie group, which is a non-finite group with a smooth topological structure ... I'll bet that clears it all up for you :-).
The article I originally cited links to this page that tries to explain what E8 is in simpler terms.
Solving the problem required 77 hours of time on a supercomputer, working with 60GB of data (compared to approximately 1GB for the Human Genome Project).
This achievement will likely have ramifications in the understanding of String Theory. The image is a depiction of the 248 vectors that make up the root system for E8.