Many thanks to Chris Tucker for producing a patch for this problem, and his description -
"
OFX import doesn't match securities with different names but same symbol.  For example, I direct-connect to download OFX and pick up a security:

<SECURITY symbol="VOE" id="922908512" name="VANGUARD INDEX FDS MCAP VL IDXVIP"/>

The security exists already as VOE with name "Vanguard Index FDS Mid-Cap Value Index (VOE)". 

mymoneystatementreader.cpp finds the existing security by ticker but the transaction import fails to find the security by name.  The following patch to mymoneystatementreader.cpp solves the problem:

*** mymoneystatementreader.cpp.orig     2013-11-24 17:27:39.959812598 -0800
--- mymoneystatementreader.cpp  2013-11-24 17:27:44.436812841 -0800
***************
*** 630,636 ****
            QList<MyMoneySecurity> list = MyMoneyFile::instance()->securityList();
            QList<MyMoneySecurity>::ConstIterator it = list.constBegin();
            while (it != list.constEnd() && security.id().isEmpty()) {
!             if (statementTransactionUnderImport.m_strSecurity.toLower() == (*it).tradingSymbol().toLower()
                  || statementTransactionUnderImport.m_strSecurity.toLower() == (*it).name().toLower()) {
                security = *it;
              }
--- 630,636 ----
            QList<MyMoneySecurity> list = MyMoneyFile::instance()->securityList();
            QList<MyMoneySecurity>::ConstIterator it = list.constBegin();
            while (it != list.constEnd() && security.id().isEmpty()) {
!             if (statementTransactionUnderImport.m_strSymbol.toLower() == (*it).tradingSymbol().toLower()
                  || statementTransactionUnderImport.m_strSecurity.toLower() == (*it).name().toLower()) {
                security = *it;
              }
"
While investigating this problem, using the CSV importer, I encountered some other issues - to follow.



Reproducible: Always

Steps to Reproduce:
1.Create an investment transaction with a new symbol.
2.Import another investment transaction using the same symbol, but a non-identical name.
3.The two should get matched, but the second was being rejected because the symbol match was failing.
Actual Results:  
As above

Expected Results:  
The two transactions should get matched.