search engine indexing and redirects

Hi all, firstly: i know nowt about search engines/crawlers spiders really. i'm giving users fake sub-domains i.e www.username.mysite.com gets redirected to www.mysite.com/users/sites/username via mod_rewrite/wildcard dns so i'm wondering if search engines will have any trouble indexing those sites. i was talking to an 'internet consultant' who has a flash red sports car and earns about 5 times more than me and he said i should look into this. i would have thought that server-side redirects are no problem for crawlers. i set up a google adwords thingy for one of the sites and it worked for a while but now they've come back to me saying the url doesn't work when it clearly does.i've asked the google folks about this and am waiting for them to get back. was just wondering if anyone had experience of this sort of thing. thanks adrian