'Invalid Argument' error message

I made the mistake of having my main table and a query open at the same
time. I also made the mistake of inputting into both tables. My guess is that
what I inputted didn't agree so I made my database go ka-put. I now get an
error message stating invalid argument. This message box pops up continually.
I have done eveything that I can think of to rectifythe problem. I have
attempted to edit and delete the discrepant line that now reads ' #Error',
but nothing works. I also get an icon (symbol) to the side of the discrepant
line that will show with a circle with a slash through it. This error
message is making it difficult for me to input data as well as run queries. I
am not proficient in SQL or access really (although some how I did create
this (what peple have told me) advanced database). So you may want to dumb
down your explanation so that I can understand the step by step of the
trouble shooting. Thanks for your help.