Imported blog from wordpress.com, all posts present, but won't display

I moved my blog from wordpress.com to a subdirectory on my self-hosted site.

http://pattyjansen.com/blog/

You’ll see that the second page of the blog will give a 404.

Facts:

– The site is Windows hosted (yeah, I know, stupid, but what did I know?)
– I’m using the same theme as on the wordpress.com blog
– all posts and images did export and are in my database. I can view them in my dashboard, but not on the blog
– editing posts does not make them appear
– I can’t “preview” those posts either
– the categories transferred and are fine
– I have the plugin yoast SEO installed, but have not changed any of the settings. This worked fine on the site in the root directory
– oh dear, make that: I can’t preview ANY posts, not even the ones that do show up on the blog
– I had a huge amount of trouble yesterday changing permalinks. My blog crashed after doing this (giving a 505 on every page), and I only managed to get it working again by overwriting the web.config file several times with a file that is supposed to fix the Windows access hosting problems.
– I changed the permalink structure to a date-less format. Maybe that is part of the issue?

Argh! I’m thinking this is not an import issue, but a continuation of the access issue.

ISP informs me that I can switch to Linux. Would that fix the problem? Would it damage my setup (of course I have backups of the blog content itself).

Thanks for any comments!