Two things to try (maybe try number 2 first to see if it fixes things, since its the easier step):
1) It looks like you have all the files, but some may have become corrupt. So...
Download the CME for IOS 124-15 zip file. Download the Cisco or other TFTP server and run on your PC. Extract the ZIP file contents and place CME GUI TAR file in your TFTP directory. Then run the xtract command from the 3825 router and pull down the CME files again from the TAR file on your PCs TFTP server.
archive tar /xtract T
FTP://pcipaddress/tarfilename flash:/
2) connect to the router by telnet and enter enable-mode. Once in enable mode, enter the following:
config term
ip http path flash:/
telephony-service
web admin system name admin secret 0 yourpassword
* replace 'yourpassword' with whatever admin password you want to set. You should then be able to logon to the GUI with username 'admin' and whatever you set for 'yourpassword'.
Hope this helps.