I have heard mixed information on this and I am now looking for clarification as it will affect the effectiveness of a build I'm currently working on. When a creature is slowed at the start of his turn, what is the absolute maximum distance he can move (excluding teleport). Please factor in everything such as if he tries to run, double moving, attacks with built-in shifting, etc. It is my understanding that he'll be able to move 2 squares total, but I'm looking for confirmation on this...
Slowed means that its speed becomes 2 if it was higher than that (Rules Compendium, page 233). That's it. Recalculate the creature's movement (including flying, walking, swimming, etc.) based on this new speed. Any powers that don't explicitly use its speed are unaffected.
For example, if a Deathjump Spider is slowed, it can still use its Prodigious Leap because even though its walk and climb speed were 6 and are now 2, the power does not refer to its speed.