will re-jailbreaking do anything to an iphone that is already jailbroken?

[farahm2]

my iphone 3g is running firmware version 3.1.2 and it was jailbroken a while ago. just recently however, cydia stopped working and the whole icon just disappeared all together. I tried that fix where you type in a series of commands in mobile terminal, but that didn't do anything, in fact after I did that the icon disappeared. I remember hearing that you can download the actual blackra1n app that installs cydia and rock, but I couldnt find it (I downloaded Rock when I jailbroke along with cydia)

So I was wondering if I download blackra1n on my computer and try to jailbreak it again, will it do anything to all the stuff on my iphone? Will I lose data? is there any other way you know how to get cydia back?

Thanks for the help.

PS, in case you're wondering why I need cydia since I already have rock, the reason is that a lot of times, sources that normally work on cydia, do not work on rock. And also rock seems very unstable because it is always crashing.

[xwinger]

just back up your phone with itunes. you've got nothing to lose...

[farahm2]

Cool, thanks!