Here is another version of the Manjushri mantra I found on YouTube:
The mantra, Om A Ra Pa Dza Na Dhi, is the embodiment of Wisdom itself. It does not have any meaning, though it is said that the five syllables after the Om are from the first syllables of the five main teachings of the Buddha. The “Dhi” is the seed syllable of Manjushri, one we visualize when we perform a deity meditation on him.
May Lord Manjushri protect all beings and grant all beings with Wisdom of Liberation!