you can also try to add these lines in your default.rdp file in Windows 7 C:\Users\YOUR USER\Documents

Code: 
bitmapcachesize:i:32000
bitmappersistcachelocation:s:\Temp
make sure
Code: 
bitmapcachepersistenable:i:1
you can even set the value
Code: 
session bpp:i:value
to 8 but the display will be a real crap

NOTE:
default.rdp is a hidden file, you can edit it with Notepad.