I recently installed a new version of licensed pymol 1.5. It works ok with small molecules (<25 kDa). But, unfortunately, I found that after I load relatively large molecules (>60 kDa) everything really slows down, movements become somewhat abrupt and etc. At the same time, I can open this molecule with coot, generate bunch of symmetry mates, add maps, but everything runs really smooth. How can I make pymol run smooth again (version 1.2 worked well before)?

Pymol: PyMOL-v1.5.0-Linux-x86_32-TclTk8.5 (I tried 64-bit with the same result)
OS: Ubuntu 10.10
Video card: nVidia GeForce 7150M
CPU: AMD Turion(tm) 64 X2 TL-62 (2100 MHz, 64 bits)