[Charles w. Southworth]

Well if its a low volume echo echo (echo) probably your best bet is to use that to your advantage. Some combination of a noise gate and judicious use of an expander will get you the best signal to ‘noise’ ratio.
Before you use the expander do some gain adjustment of the overall audio, DOWNWARD, and then expand the remaining areas. (use a conservative ratio probably between 1.5 and 3)

As previously mentioned, if you have the option of adding on some noise, you can mask a lot of low volume sounds from listeners ears.

Another thing thats worth a shot: If the echo has any kind of frequency localized resonance, find it and use a fairly high Q to reduce just that portion of the audio. (Q greater than 4) That one though will depend on two things, first does the exist in the audio and second do you have the ears for it?

If you have time, Soundhack has some items that can probably help you. But it being a few days since your posting, probably not. (There again, you will need ears most video people lack.)