Gigabyte CMOS & Memory

HI! I have some serious problem with my secondary computer so I realized I should be fine to ask you if you dont know how to solve it. I have Gigabyte 7VT600-L, few week ago I woke up started computer and there was a CMOS CHECKSUM ERROR message, so I was surprised wtf is that because it worked perfectly a day before. It wasnt to only thing that was going on. Every time I unplug my computer from electricity and then try to start it. It says I have only 256mb of RAM ( but I have 1GB), then I just shut it down with a button before it starts booting system, try to start it again... still 256mb RAM, shut down and start few times and wtf? 512mb of RAM. I dont understand. When I start it & shut it down few time like that it goes normally 1GB but theres a CMOS CHECKSUM ERROR MESSAGE. When a continue to boot system and try to work with 256 or 512 of RAM, computer doesnt display CMOS CHECKSUM ERROR. but workd totally slow like a crap. I have 2x512MB RAM KIngston 400Mhz CL3. I tested ram in other computer and works fine. I also read tons of forums about CMOS CHECKSUM ERROR and I tried to change the battery and it didnt solved the problem. DO you have any ideas?

board caps? dunno whats that and how to check it...