求救，C#+ACCESS用一段时间就出错 - .NET技术 / C#

各位大哥大姐，我做的单位的一个简单的办公系统用一段时间（或许一二个星期、或许三五天不定期）出现错误，不知如何解决（重启服务器后正常）请各位帮帮忙，谢谢。

以下是IE上显示的错误信息：
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Server Error in '/oa' Application.
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未指定的错误 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Data.OleDb.OleDbException: 未指定的错误

Source Error: 


Line 60: string connstr="Provider=MicroSoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("#sdfsdf44564sfds3f45sdfwefs36sdfsdfd.mdb");
Line 61: conn=new OleDbConnection(connstr);
Line 62: conn.Open();
Line 63: string sqlstr="select * from members where Usernames='"+yhm.Text+"' and Userpwd='"+mm.Text+"'";
Line 64: cmd=new OleDbCommand(sqlstr,conn);
 

Source File: d:\oa\default.aspx Line: 62 

Stack Trace: 


[OleDbException (0x80004005): 未指定的错误]
  System.Data.OleDb.OleDbConnectionInternal..ctor(OleDbConnectionString constr, OleDbConnection connection) +271
  System.D