my import button is no0t working!!!

i can export but when i click AT IMPORT…its just gets clicked and the import box doesnt apear…
i have
vista 32 bit…
4 gb ram ddr2
9800 gt 1 gb ddr3
dual core 3 ghz…
help help help

Which version of ZBrush is it?
What plugins have you installed? Or other ZStartup content?
Have you run a system scan for viruses?
hey aurick ty for replying…
i was using 3.1 but was geting the same problem…
but now i m usuing 3.5…its all fin for 2 or 3 days…then boom again the same problem hapend…
ther is no plugin instaled…
NO i did not run virus scan.
i dint understand zstartup content…i have not done any changes in this folder…
pls help me…
ty again