I am very new to xoops, much more familiar with phpnuke, but im really getting into the abilities of xoops, and have jjst started to really play with it. now last night i installed alot of new mdules, agenda-x being one of them. last night that module worked great. now today the calender does not load at all. i have uninstalled it and reinstalled it alot and it doesnt fix it. so i thought maybee the calender was broke for whatever reason, so i installed a differnt calender, and same results. only calenders are having this prob. any thoughts?

Switch on PHP debug mode in preferences.
If you get a header problem would be on the last couple of line of the debug output check for "spaces" after the ?> in the referred php files. I had a similar problem with agenda-x and various modules, removing the spaces fixed it for me.

Also look into the XOOPS FAQ in the debuging and faults section.