I was having some issues with the front end editor when JoomSEF is enabled. First it was giving me an error when I tried to save an article using the front end editor...it would say the alias is already being used and would not save my changes. This happened for any article. I updated to Joomla 2.5.1 and now the front end editor will not even come up when JoomSEF is enabled. Please help!

Hi,
Thank you for your report, it seems that Joomla 2.5 has changed the handling of edit URL. We'll fix it in next version.
In the meantime, go to JoomSEF -> Manage Extensions -> Content -> Common tab and set "Do not SEF URLs matching regular expression" field to "view=form" (without the quotes).

Thank you! This fixed the issue of the editor not coming up but I'm back to the original problem I was troubleshooting. When JoomSEF is enable and I edit a article and then save it I get the error:

Save failed with the following error: Another article from this category has the same alias

How can I fix this?

Maybe I've found a problem. Try the following configuration in JoomSEF -> Manage Extensions -> Content -> Common tab:

Custom non-SEF variables: a_id
Do not SEF URLs matching regular expression: (task=article.edit)|(view=form)

Then go to Manage SEF URLs page and set Real URLs filter to "a_id=" (without quotes) and delete all the filtered URLs.

Please let me know if it helps.