I am using wordpress 2.6.2. I got little problem while saving posts. Save and publish buttons does not working when you use custom field. Initially I thought some plugins are causing the problem then I installed fresh wordpress without any plugin and tested got same issue.
here are the steps to replicate the problem
1) Create a new posts
2) Copy a post say from bbc news page
3) insert tags
4) add a custom field name thumb value <img src="http://myimage.com/img.gif" alt="" /> click on add button
5) here you will see wordpress adds slashes into images and it no longer works
6) copy image code again from step 4 and update it this time it work and click on save or publish button they both will no longer work.
Some times it makes me nut when I forgot about this bug :( Please fix this problem.