The login box will prevent the spider from crawling anything that you have to login to see, however, this will not prevent it crawling the rest of your site. I have several asp sites with logins and they all rank well.
Basically spiders read whatever a human could read, so as long as you don't need to log in to actually view the page there should be no problem. Are the spiders visiting you? Have you submitted? Are you lined to from other sites? There could be many reasons for not being list. Have a read through these fora as there is a wealth of information here to help you.
Also, we have had quite a few discussions recently about asp pages and engines, if you have a look through the Google and Scripting fora for the last week or so you will find some interesting reading.
PS., have another read of the user agreement for this site as well as self posting URLs is a no no. Better to put your site in your profile and refer to your profile in your posts. Cheers, Woz ;)
Being an ASP page wont really alter how well it gets indexed. It does not matter how the page is rendered (ASP, PHP, CF) it will still be indexed, if it is designed well enough.
I have page listed that produces dynamic links to dynamic pages, no problems. Providing you submit the default URL and not a specific page you will be able to change technology without too much greif. EG submit www.abc.com and not www.abc.com/default.asp
You main priority should be content that is indexable. I had a quick glance (had to be quick i am work and it is a male escort site :-)). Maybe it is there but i didnt see it you could tie down a location, as "escort service" is very vague but include Birmingham as well and you narrow down the competition for what is probably a popular phrase.