The Symbian version of MusiKloud has now been updated to version 1.5.2. This release is simply a fix for the authentication errors caused by a problem with the SoundCloud SSL certificates. The update can be downloaded by going to Settings -> Update in MusiKloud.
As it is no longer possible to sign Symbian SIS packages, the application UID has changed for MusiKloud 1.5.2. Unfortunately, this means that you will lose the archive database, as this is stored in the application private folder (generally C:/Private/$UID, or in the case of MusiKloud C:/Private/0x20068c6a). The only way to prevent this is to gain read/write access to these private folders and copy the database file from C:/Private/0x20068c6a to the private folder of MusiKloud 1.5.2 (C:/Private/0xe561675f). This may only be possible with custom firmware.