Changes to internal architecture of the 10.1B client code and 10.1B database internals have changed the memory requirements and some functional limits for many executables.
In 10.1Bx the client will most likely only be able to connect in shared memory to a database whose total allocated shared memory is around 1.4 Gig of RAM (or less).
Depending on parameters used to start the database the following are the values typical for -B dependent on database blocksize:
DB Blocksize Approximate limit for -B value which
will allow shared memory connection
These numbers are largely approximations.
Changes to .dll versions within a system may increase or lower these suggested values.
Changes to some startup parameters which affect shared memory such as -B, -L, -Mxs, -shmsegsize, et al. will likely alter the above limits.
Though the database may be able to startup with values higher than those listed above, the client requires a much larger heap size in 10.1B compared to earlier versions and this added memory usage lowers the total memory that the client can attach to and still be within the addressable 32-bit memory limit for a client executable on Windows.