To get good performance you need to go the VPS route ... there are several that offer managed service with Cpanel and all .... Shared hosting is unpredictable even from reputable hosts because you are at the mercy of your next door neighbor
I can suggest you to Dreamhost. I am working with them and have 8 website on one hosting package. Some of them small web sites and some of them medium. Never had any problem with them. Also i can give you a promo code if you want, so you can get almost %50 price cut down.
Save your money, most small forums run on shared hosting just fine. Sure it is possible for shared hosting to go offline from time to time, but most maintain an 99.8/99.9% uptime (better than my Comcast cable internet ).
As Dean said, try talking to your hosting provider. Namecheap (yeah, they also have hosting) listened to our problems over at a forum I'm a moderator on. Although it took 24-hours.
Urljet is good for small forums. They give you vb and xf related support too. I also recommend asmallorange. For large sites, I really recommend ServInt. They are really good. I am with them now even if my sites not really that big.