I was upgrading a solution from 6.2 to 7.2 and it had a number of custom fields that no longer worked, so I started to fix the code.
One of the custom fields showed the SPEAK Insert link dialog and after making a lot of changes, I noticed that I had broken the SPEAK dialog, see below
I reviewed the changes I had made, and could not see what could have caused this issue? But to be on the safe side, I undid all of my changes, did a full build, etc and still I had the issue 😦
So I tried to open the dialog from a sitecore standard field, and it was also broken 😦
Whist starting to panic, after 5 minutes I noticed that the dialog had fixed itself!!!!
It appears that after a restart of the website the first time you open the “Insert link” dialog you have to wait 5 minutes for it to start working, after that it works straight away.
Since SPEAK in 7.2 uses a similar setup to Sitecore 8, you may be experiencing Razor compilation times that might be helped by some of these tricks – though I don’t think 7.2 has the precompiler. http://kamsar.net/index.php/2015/02/sitecore-8-experience-editor-performance-optimization/
Cheers for the link