take a look at this thread if you haven't tried searching. I know you are new and probably looking for any fix. you cant panic here. your going to have to search and read.
in the thread I posted, or any thread, pay attention to the stats of some of the folks posting. you may pay attention to some of the more experienced folks.
I don't know some of the specifics as you did not mention. many factors come into play. you will see talk of what carrier..... it is important
what rom are you currently running or have installed?
how clean is your process of flashing?
how experience are you?
some in the thread are talking about modem......as one posted, "changing your modem is not going to fix problem", he is correct.
I have ran into many problems, only saw SIM message show when I had no SIM in phone. always the failsafe solution has been returning to stock and start over.
you would not be the first person to rush off and think, "im flashing my phone, look at me, im cool". doesn't work like that.
I have always been the more cautious one. I read and make sure I understand. I have all my files in place. heck, I have evan rehearsed the process.
maybe so, but I have yet to have a problem I couldn't figure out.
could be a "fix permissions" issue
could be a "format system" issue
some developers have specific instruction for flashing their rom, any deviation could cause a myriad of problems.
again, look at experience levels of some of the posters.
keep us informed as people are reading, but you haven't given any specifics. you have told us what your problem is and what you need fixed, but didn't tell us how you got there.
need that if you want help