Magento1 createBlock method returns "bool(false)" in livehost

Your action code should be

public function minhaactionAction()
    $block = $this->getLayout()->createBlock('slideproducts/slideproducts');

I suspect that versions of your Magento in localhost and live versions are different.

After Magento version 1.9.1, Magento introduced a new feature of block permissions.

Now if you are introducing a new block class in Magento system, you need to allow it from:

System -> Permissions -> Blocks

Click add new block where block name slideproducts/slideproducts and isAllowed -> Yes

Now save. Clear cache. Hope this will solve your problem.