Pom.xml errors in Wicket

Hello, I am getting an error:

Missing artifact org.apache.wicket:wicket:pom:6.15.0:compile

This is when I try to update to 6.15.0 from 1.5.5 .. I also get it for
slf4j.. Here are the two errors together:

7/8/14 11:01:51 AM CDT: Missing artifact
org.apache.wicket:wicket:pom:6.15.0:compile
7/8/14 11:01:51 AM CDT: Missing artifact
org.slf4j:slf4j-api:jar:1.6.4:compile

I can't understand why. It does this even if I change it to 6.12.0 for
instance. What can I do to troubleshoot this, I don't get what would cause
this issue. Here is my pom..

<properties>
<wicket.version>6.15.0</wicket.version>
<jetty.version>7.4.0.v20110414</jetty.version>
<log4j.version>1.2.16</log4j.version>
<slf4j.version>1.6.1</slf4j.version>
</properties>

<dependencies>

<dependency>
<groupId>org.apache.wicket</groupId>
<artifactId>wicket</artifactId>
<version>${wicket.version}</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.apache.wicket</groupId>
<artifactId>wicket-datetime</artifactId>
<version>${wicket.version}</version>
</dependency>
<dependency>
<groupId>org.apache.wicket</groupId>
<artifactId>wicket-extensions</artifactId>
<version>${wicket.version}</version>
</dependency>
<dependency>
<groupId>org.apache.wicket</groupId>
<artifactId>wicket-ioc</artifactId>
<version>${wicket.version}</version>
</dependency>
<dependency>
<groupId>org.apache.wicket</groupId>
<artifactId>wicket-spring</artifactId>
<version>${wicket.version}</version>
</dependency>

<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.16</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>${slf4j.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>${slf4j.version}</version>
<type>jar</type>
<scope>compile</scope>
</dependency>