Does the problem persist if you disable/remove all 3rd-party plugins?
eg. from your err.txt file, these are the 3rd-party plugins you've installed:
gen_lyrics_ie.dll (lyrie121.exe is the setup file)
Apart from that, either try (WinXP Pro) right clicking on the "Program Files\Winamp" folder, select Properties, then the Security Tab. Give all users access to Modify and Write in the Winamp directories, sub-directories, and files (note: you may need to Disable Simple File Sharing
or (WinXP Home) install Winamp to the Shared Documents dir (C:\Documents and Settings\All Users\Documents),
or try installing the Winamp Profiler
plugin instead (allows multi-user settings).