SilverTail

Opened client, problem not presenting, activated resource pack, still no issue.
Closed client, relaunched with resource pack activated, problem now present.
Deactivate resource pack, problem still present.
Deactivate resource pack, close, relaunch, issue gone again.

Same issue, without a resource pack activated.

Still experiencing this in 1.5.2. When looked at and angered, the Enderman will rush the player, but after the player attacks once, will teleport away forever. This makes it difficult to kill an Enderman and harder still to attain Ender Pearls.