Problems Reading a .xlsx file?

Question

I made a test file, and ran through the excel file just fine, but whe nI insert one with a lot of data, I get the following error:

The Microsoft Office Access database engine could not find the object 'Sheet1$'

Which seems incredibly obvious, but 'Sheet1' is surely there, just like in my test file - I have checked about 30 times. There is only data on the first Sheet and it is clearly named 'Sheet1' like the default. Any idea why I would still be getting this error?

code:

string path = Server.MapPath("~") + "\\attachments\\ejmaps\\ejmaps.xlsx";
string connString = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=\"Excel 12.0 Xml;HDR=YES\";");
OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * FROM [Sheet1$]", connString);

Answer 1

odd... I had changed the name back to what it was originally (EJMaps Pull.xlsx) and it worked?

Any ideas why that would be?