This is a really strange issue and not sure what is causing it. We have a links module that we display on all pages of the website. In DNN 5.5, when a user adds a link then clicks update the site just hangs there. If they navigate back to the page you can see the link was indeed added but every time you add a new link it does the same thing, just hangs after you click update (even though it has been added). 

This was not an issue in DNN < 5.5 (5.4.4 was fine). and this only happens if the module was added to all pages. If we just have a links module on a single page adding the link behaves as normal. It only hangs if the module was added to all pages. Not sure if this happens with other modules or just the links module as the links module is the only one that gets displayed on all pages.

Has anyone else experienced this? Any idea of a fix or work around? 

Both. We upgraded a test site to 5.5.1 to verify it was happening in there and it still is.

A site running 5.4.4 (same web server and db server and same configuration as the other sites) has no issue. Verified this on four 5.5.0 sites against two 5.4.4 sites and a 5.5.1 site.

We do not use multiple languages nor do we have any languages besides English (United States). Also, localization is not enabled.