There's two specific chunks that won't load in my server. I tried to change the render distance and relog, and it doesn't work. These two chunks are parts of my base, so, if it is possible to keep them, please help me.
OK, looks like you really do have some problematic chunks, lets see if we can fix this.
1. Backup your world!!!
2. Download MCedit (http://www.mcedit.net/)
3. Launch MCEdit
3.5 Load your world
4. Press 'ctrl-i' and select 'Repair regions' in the dialogue which pops up
5. Once this has completed, save your world and exit MCEdit.
6. Start Minecraft and load up the map and see if it worked.
Dont think so, those parts got corrupted and thus not showing chunk at all (also mod blocks are problem in MCedit, so it might loose some). I recommend making regular backups, only way to be sure you get all back. If you have server, there are mods that can make regular backups in time interval. Also Ive seen some tricks to do it in SSP, but dont really know much about it...