@nornen: I agree with you. However, I do not know what exactly the difference is. Maybe I need to read more articles in Esperanto in order to improve my language sense. Thank you for your detailed answer.

Tempodivalse:

"Ŝi vidis lin kuri."

I would advise not to use the infinitive here to say "She saw him run".

But this construction is commonplace. That in parallel sentences the accusative preceding the infinitive may be the object of the infinitive does not lead to confusion.

Ĉu vi volas min helpi means Ĉu vi volas helpi min (pace Nornen). But this does not mean that Ŝi vidis lin kuri could be interpreted as Ŝi vidis kuri lin with lin being the object of kuri.

sudanglo:But this construction is commonplace.

Yes, absolutely nothing wrong with that form.

From the Fundamenta Krestomatio: "Mi jam tute kutimis vidi vin forkuradi al baloj, diris la komercegisto"

The use of the infinitive will often be preferable to the participle if you want to avoid stressing continuation of the action. E.g "mi vidis lin kuri en la domon" suggests that he got inside. Using the participle would imply you only saw him running part way up to the house.

When the infinitive is used the action is viewed as a whole. With the present participle the action is presented as ongoing. The infinitive may be therefore be more appropriate in cases of actions that are instantaneous, do not have temporal extension.

Mi vidis la teroriston mortpafi la ĵurnaliston (mortpafanta la ĵurnaliston might sound a bit odd).

On the other hand Mi rigardis lin leganta(n) la Biblion sounds better than Mi rigardis lin legi la Biblion

However, when the infinitive is used it may depend on context and on the actual verb as to whether the implication is that the action is completed.

Kaj enirinte en la tombon, ili vidis junulon sidantan ĉe la dekstra flanko

The above may be rewritten as ili vidis junulon, kiu sidis, but would you say ili vidis lin kiu sidis.

sudanglo:When the infinitive is used the action is viewed as a whole. With the present participle the action is presented as ongoing. The infinitive may be therefore be more appropriate in cases of actions that are instantaneous, do not have temporal extension.

I agree. This is what I tried to express by:

Mi mem:In summary I think there is indeed a difference between the use of a object predicate and a complex (verbal) object.
Mi vidis lin kuranta. = Mi vidis lin kaj li kuris.
Mi vidis lin kuri. = Mi vidis, ke li kuris.

An example where the difference may be stronger:
Mi vidis lin eliranta la oficejon. = Mi vidis lin, kaj tiu-momente li proksimigxis al la pordo. Tamen mi ne certas cxu li finfine eliris la oficejon.
Mi vidis lin eliri la oficejon. = Mi vidis, ke li eliris la oficejon. Sendube li eliris gxin.

The fact that the action is viewed as a whole, when the infinitive is used, seems to validate my interpretation that in this case the infinitive is not an object predicate but the whole infinitive phrase is the direct object of the matrix verb. Contrarily to how Bertilow analysis it in the PMEG.

Basically:
Mi vidis lin kuri. = Mi vidis lian kuradon. The object of vidi is the act of running (whose subject is the runner).
Mi vidis lin kuranta. = Mi vidis lin dum li kuris. The object of vidi is the person, and as an additional information the predicate noun states that this person was running.

Am I making any sense?

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On a side note: The Mayan-K'ichee languages which lack infinitives use exactly this construction.
(intransitive verb) EO: Mi vidis lin kuri. = Kek: Mi vidis lian kuradon.
(transitive verb) EO: Mi vidis lin ĉasi ilin. = Kek: Mi vidis ilian ĉasadon por li.

tommjames:

sudanglo:But this construction is commonplace.

Yes, absolutely nothing wrong with that form.

From the Fundamenta Krestomatio: "Mi jam tute kutimis vidi vin forkuradi al baloj, diris la komercegisto"

The use of the infinitive will often be preferable to the participle if you want to avoid stressing continuation of the action. E.g "mi vidis lin kuri en la domon" suggests that he got inside. Using the participle would imply you only saw him running part way up to the house.

Perhaps I am unduly influenced by Slavic langauges again, but I would have used Mi vidis, kiel li kuris en la domon (parallel to Я увидел, как он вбежал в дом) to express this sense of completion - or, perhaps, Mi vidis lin enkurantan en la domon, where the en- clarifies aspect.

Not saying that the infinitive is wrong ... just that it sounds a bit odd to my ears, and I don't see it *that* frequently.