It's not only from the market, you will get a reboot anytime you try to install anything. I'm not exactly sure of why, and as far as I can tell the only way to fix it is to wipe data/cache and reload the rom.
The only thing I can think is that when you restore data to ANY app it may begin to mess up. When I had the issue I reloaded the Rom and did not restore any data or apps, I just let the market restore everything. Then I loaded my theme(evolution) and ran it for a while. Then I loaded a update.zip that I made that changes the animations and the progress bar to green, then I ran that for a while. Then a kernel, I checked the market between everything and it continued to work.
It may be coincidental, but It has worked all week. It did't work the next day after I flashed 1.1.7.0. The only thing I did different is not restoring app data. I did however still restore system data (desktop layout, sms, call log).
Everything seems to work pretty well on this version. The music player will stop playing when I am using the navigation. And every once in a while the laucher force closes in the background (probably because I restored the layout). It fly's and I get great battery life with the chevy ulv 1100 kernel clocked to 1000, so I can deal with those issues for now.