There are several known issues with installing service pack 2 on server 2003, most of these are network related.  These problems are not common, but it is possible you may experience one or more of the issues. Some include:

• Inability to remotely connect to the server using Remote Desktop, Remote Web workplace, and using a Windows VPN ( usually an 800 error).
• Local clients cannot; access shares, join a domain, access Exchange, browser problems accessing FTP and secure sites.
• Performance issues such as slow logons and poor performance accessing network shares.
• Problems with DHCP and ISA services.