Question
I upgraded our exchange version to match the customers ( 5.0.1.4032 ) and following a restart of the server I am also now not able to delete signatures; I was able to in the previous release that I had installed 5.0.1 3982
Solution
1. Confirm that version of IIS component is "4032"
https://<myserver>/MailSignature/IISStatus
2. Navigate to the folder on your IIS server : C:\inetpub\wwwroot\MailSignature\Views\SigBlocks
3. Rename the old index.cshtml to index.old
4. Replace with attached file
PLEASE NOTE: A Server Restart is NOT required for the above.