from what you wrote, I guess that the problem is within the configuration.
(Which would explain why a reinstall does not help.)
Which version of Gpg4win are you using? (The current one?)
Does Kleopatra work? (Which is your alternative.)
Did you change any settings recently (around the time it was working)?
If you have a backup, you could compare the configuration files
from the backup with the current ones and see if there is a difference.