Hi Nason,
Does the Editor use this feature regularly and it only happened today? Or do they use the library rarely and they only discovered it today? ie. could have been a problem for a while now.
If there's been no code changes for FarCry its either an environment issue with IIS/OS or there is some data changes which is causing a problem.
## data issue
I'm not sure how a data issue would affect the library picker -- it should generate an error rather than a 404. Perhaps the error itself is being redirected.
If you call the same URL (ie including parameters) in a separate window do you still get the 404? Has the browser been redirected to an alternate page? (possibly a missing error handler?)
If its a framework error we need to try and find it -- so if we can't work out if the facade call is redirecting you might check the CF logs.
## Environment issue
Check your IIS settings; especially rewrite rules that may be causing a problem.
Hope that helps,
GB