I'm using the following to import the calendar:
curl -u user1@brockport.edu:test123 --data-binary @/tmp/user1.ics http://zimbra1.brockport.edu/service...lendar?fmt=ics

<html><head><title>Apache Tomcat/5.5.15 - Error report</title><style><!--H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}A {color : black;}A.name {color : black;}HR {color : #525D76;}--></style> </head><body><h1>HTTP Status 500 - </h1><HR size="1" noshade="noshade"><p><b>type</b> Exception report</p><p><b>message</b> <u></u></p><p><b>description</b> <u>The server encountered an internal error () that prevented it from fulfilling this request.</u></p><p><b>exception</b> <pre>java.lang.ClassCastException: com.zimbra.cs.mailbox.calendar.Recurrence$Exceptio nRule
com.zimbra.cs.mailbox.CalendarItem.updateRecurrenc e(CalendarItem.java:219)
com.zimbra.cs.mailbox.CalendarItem.processNewInvit eRequestOrCancel(CalendarItem.java:789)
com.zimbra.cs.mailbox.CalendarItem.processNewInvit e(CalendarItem.java:603)
com.zimbra.cs.mailbox.CalendarItem.processNewInvit e(CalendarItem.java:582)
com.zimbra.cs.mailbox.Mailbox.addInvite(Mailbox.ja va:3112)
com.zimbra.cs.service.formatter.IcsFormatter.saveC allback(IcsFormatter.java:134)
com.zimbra.cs.service.formatter.Formatter$SaveOper ation.callback(Formatter.java:273)
com.zimbra.cs.operation.Operation.schedule(Operati on.java:190)
com.zimbra.cs.service.formatter.Formatter.save(For matter.java:103)
com.zimbra.cs.service.UserServlet.doPost(UserServl et.java:438)
javax.servlet.http.HttpServlet.service(HttpServlet .java:709)
com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:162)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)
</pre></p><p><b>note</b> <u>The full stack trace of the root cause is available in the Apache Tomcat/5.5.15 logs.</u></p><HR size="1" noshade="noshade"><h3>Apache Tomcat/5.5.15</h3></body></html>

Web logs weren't much help. Were running version 4.5.6 . Also, is there a way to delete this user's calendar and create a new one? Thanks for your help