I'd say
you should get rid of the ODBC-JDBC bridge first. Sun/Oracle had always suggested to use native drivers when available, and there certainly are native drivers for MS SQL. There were known issues with ODBC-JDBC last time I checked, and since virtually every database has a native driver, nobody is going to fix them.
So my suggestion is to switch to native drivers and see whether the issue persists.
Setting fetch size is a good idea anyway, I'd say a reasonable one-size-fits-all value could be around 100. Only if you read really wide tables (several dozens of columns), a lower value might be better. As always, you should
test the new setting thoroughly.