Form the manual:

"If the escape attempt fails, the acting hero remains engaged and cannot attack when his next turn to act comes."

So if the escape attempt fails, can the hero make a non-attack action (like "Rally Comrades") the next turn?

The rules only preclude making an attack, so I'd certainly allow them to make any non-attack action the next round.

I wouldn't allow a Combat Task in that situation.

- You're meant to have lost something for failing.

- To quote the rules on your example of Rally Comrades:
"When it is his turn to take action, a hero may forego his chance to make an attack roll and make an Inspire or Song roll instead."
If a failed Escape Attempt means you cannot attack, then you don't have a "chance to make an attack" to forego, so you don't qualify for that Combat Task.

But other -- more peripheral / less combat-beneficial -- uses of skills might still be possible.

Cheers,
--Os.