Wordpress-based website front page not updating for everyone

TPSou

I know it's not great etiquette to post links on here so I won't, but my website is based on wordpress (the 2011 theme) and up until the last couple of weeks, whenever I added a new post I could just give out a link to the main site and everyone could see the new posts at the top. For the last two posts though some people can see them and others can't, they just don't appear on the homepage. I've checked to make sure they're not set to private or password locked or anything silly like that, but I'm not really sure what else to look for. On my PC it all works fine so it's hard to test!

So my question is: How can I work out why new posts aren't appearing for some people, and then how can I fix it?

Edit: Until the problem is fixed I'm using a caching-based workaround but it's not ideal.