As I have suggested many times to ppl... you might want to post @ Howardforums... you might be able to get better support, as there are not as many regular posters at this site compared to Howardforums (including myself, I check that site Daily, yet this one not even weekly).
I would suggest performing a hard reset (wiping all data including apps).
If this does not work you can try rooting and flashing a new Rom. Might resolve your issues.
I had the same problem with my daughters Captivate. Rogers tech support asked us to to a factory reset. When that didn't solve the problem, they replaced it under warranty.
Not sure if Howardforms is for everyone. Looks to me like the answer there for everything is "root and flash". Of course that just leads to new issues.
You are not really a good ambassador for that site. I would prefer not to deal with people who "roll eyes" at what they think is my opinion.
its is vey challenging to root the captivate, i have one and rooted. but that is not an answer to a problem with a phone, best bet is talk to tech support, find out what your options are. maybe look into the avg app for your phone (anti virus) its great. make sure you read all that the apps can do with your phone before installing, some apps that are captivate ok, will crash the phone causing it to "soft" reset. if it goes black and vibrates once, then a couple seconds later it vibrates twice, it has a app crashing.
Give rogers a call and speak with tech, they will try to resolve the issue and if it can't be resolved then they will have you send out your phone for repair and provide you a loner phone. If a loner phone is not available (tried 14 stores and no loner phones) then call them back and they will send you a replacement phone for a $35 fee. This is what happened to me but my issue was my lock/power button was acting on its own.