Magento Product Tags Keep Disappearing

I am running Magento 1.5.0.1 and I have been tagging my configurable products in the administration section, i.e. admin > catalog > tags >开发者_开发问答 all tags > add new tag > products tagged by administrator

The problem is that after reindexing the tags go all messed up. i.e. products disappear from tags, products appear in tags that where not added, and all this occurs randomly, not all products disappear from the tag. please note, the products don't get deleted, just the tagging information.

I am editing it from Google Chrome.

Any ideas why this is occurring and a solution?