Links to Posts don't always work

Hi I’m relatively new to WordPress and have come across a problem that appears on a number if sites I run.

Basically when someone does a post the link to the post doesn’t work. Although it shows that I have posted something to the site you can’t actually view the posting.

Now this doesn’t happen every time a post is done and I have narrowed it down that if the post is gone in and out of a few times ie it has been saved as a draft at least once then the link somehow breaks.

This isn’t a major issue as I can copy the whole post and repost.

Any suggestions – is this something to do with permalinks?

Thanks in advance!!