Default weired thing with elf canot complete dial number...

weired thing with my efl.
it hapens to me that sometimes i canot call someone, it tels me that the dial number canot be completed becouse its incomplete or there is no signal, thing is i have lots of signal and i can recive cals. if i soft-reset the phone everithing its ok. it hapend to me twice today and every time i checked the call log i had a missed UNKNOWN call. and afther that i canot dial... has any one experienced something like that ?

ps i have the elf and latest onyx rom.