did you see into log file? (/Logs)
How did you solve it? Others might be getting the same error.
And by "others" I mean....ME!!!
Open Web.config. Set stdoutLogEnabled to true (L:14). Then check error log in ~/Logs folder.
Yup - that did it. Was finally able to see error details and then work on solving my particular problem from there.
(note: probably not the same as your particular problem so I won't go into the sorted details here. )