Xvesa freezes the computer - no log file?

Hello again... :D
My config
kernel 2.6.5 vanilla on FC1.91 (custom yum udpate) on a P4 2.4C, 512Mb RAM 
and a GeForce FX 5200 128 Mb
My last two CVS checkouts haven't worked at all. If I run
Xvesa -screen 1024x768x32x85 -shadow :1 & xterm -display :1
or -screen 800x600x16x85 -shadow :1 ... (same syntax)
the screen goes blank and no input is accepted (basically it freezes...) 
except that any other running task continues, which means that the system 
hasn't crashed. tasks and ACPI events work fine but I cannot change the 
terminal (ctrl+alt+f1 thru f8)
any resolution to this problem?

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