ssgjcl - 8:51 pm on May 20, 2010 (gmt 0)

I don't know much about flash, so I can't tell you what Google sees in your flash.

Being linked form abc.com shouldn't be negative for xyz.com since the splash page just contains two links. (it's no link farm)
It is more of a problem for www.abc.com/default.aspx since the homepage isn't the start page of the domain.

In your situation will marketing abc.com not benefit xyz.com in any way. (unless Google can actually read something in the flash)

The not caching, do you mean the site isn't in the index? If that's the case, are there any links to xyz.com or did you submit it to Google?
If those link do exist, and the site isn't new, there might be another problem why Google doesn't index it.
If there is no way Google can know xyz.com exists, then, well tell them.
If xyz.com is just not in the Google cache, it might be a time issue (it takes a while).

Why not make on both domains homepages a link to the other (maybe with a nice text/picture) and get rid of that splash page? Neither Google nor your users like flash, and then both sites will be link-partners, promoting each other.