connection with license server failed

HI all

     I have encounter this problem:connection with license server failed,could somebody help me to solve,thanks.

The structure like this:one head quarter db and sereral sub company db(about 14 sub db).

the programm is to copy item master data from the hq db to sub company db using DI api.

the error show up when I connect to the sub company db randomly,

for example,first connect to the sub db,I have 2-3 sub db shows the error,the other db works fine.

the second time to connect to the sub db,also 2-3 sub db shows the error,but not the same with the first time,

I am very sure the paramet is correct.have somebody met this situation?

the code I use below:

                oCompany = new SAPbobsCOM.Company();   

                oCompany.Server = subDBServer;

                oCompany.DbServerType = SAPbobsCOM.BoDataServerTypes.dst_MSSQL2008;

                oCompany.language = SAPbobsCOM.BoSuppLangs.ln_English;

                oCompany.UseTrusted = false;

                oCompany.DbUserName = subDBUserName;

                oCompany.DbPassword = subDBPassword;

                oCompany.CompanyDB = subCompanyDB;

                oCompany.UserName = subUserName;

                oCompany.Password = subPassword;

                oCompany.LicenseServer = SubLicServer ;

                lRetCode = oCompany.Connect();