No hotfix is without side effects. KB968730 had documented caveats:
WindowsXP-KB968730-x86-PTB.exe.: Prevents Event ID 13 errors where systems fail to enroll for certificates because the CA uses SHA-2. windows xp kb 968730 x86 ptb hotfix
: Fixes many "Invalid Certificate" or "Site not trusted" errors in older browsers like Internet Explorer 8. Windows XP KB968730 x86 PTB Hotfix — Complete
: Windows XP Service Pack 3 (x86) and Windows Server 2003 Service Pack 2 (x86). Double-click WindowsXP-KB968730-x86-PTB