Gennady: Or do I increase the buffer in 1.8.2, and the IDE takes the Hardwareserial.h file from 1.6.5, which is also installed by me?
As a piece of English that makes no sense.
And if you have two versions of the IDE on your PC they will be completely separate. You can use whichever you choose. Recently when I needed a bigger serial input buffer I just made a copy of the IDE with a different name and changed the buffer size in that, Now I can use whichever version suits my requirement.
If you have a buffer that is bigger than the message that is being sent then I can think of no technical reason why the message cannot be parsed. However I know nothing about the UBLOX library you are using and that is where I would start searching for the problem.
Please post a link to the datasheet with the specification for the data that is SENT by the GPS device.
An example of a typical message would also be a big help. If it contains non-printing characters be sure to identify them all. They can be the key to effective parsing.